For the three months ended March 31, 2009 and 2008.

The following information should be read in conjunction with our unaudited condensed consolidated financial statements and accompanying notes included in this report. The following information and such unaudited condensed consolidated financial statements should be read in conjunction with the financial statements and related notes, together with our discussion and analysis of financial position and results of operations included in our Annual Report on Form 10-K for the year ended December 31, 2008. Our financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP").

Key References Used in this Quarterly Report

Unless the context requires otherwise, references to "we," "us," "our," "the Partnership" or "Duncan Energy Partners" are intended to mean the business and operations of Duncan Energy Partners L.P. and its consolidated subsidiaries.

References to "DEP OLP" mean DEP Operating Partnership L.P., which is a wholly owned subsidiary of Duncan Energy Partners through which Duncan Energy Partners conducts substantially all of its business.

References to "DEP GP" mean DEP Holdings, LLC, which is the general partner of Duncan Energy Partners.

References to "Enterprise Products Partners" mean Enterprise Products Partners L.P., which owns Enterprise Products Operating LLC ("EPO"). Enterprise Products Partners is a publicly traded partnership, the common units of which are listed on the New York Stock Exchange ("NYSE") under the ticker symbol "EPD." EPO, our Parent, owns our general partner and is a significant owner of our common units. References to "EPGP" mean Enterprise Products GP, LLC, the general partner of Enterprise Products Partners.

References to "TEPPCO" mean TEPPCO Partners, L.P., an affiliated publicly traded partnership, the common units of which are listed on the NYSE under the ticker symbol "TPP." References to "TEPPCO GP" mean Texas Eastern Products Pipeline Company, LLC, which is the general partner of TEPPCO.

References to "Enterprise GP Holdings" mean Enterprise GP Holdings L.P., a publicly traded affiliate, the units of which are listed on the NYSE under the ticker symbol "EPE." EPGP and TEPPCO GP are both wholly owned by Enterprise GP Holdings.

References to "EPCO" mean EPCO, Inc., which is a related party affiliate to all of the foregoing named entities.

All of the aforementioned entities are affiliates and under common control of Dan L. Duncan, the Group Co-Chairman and controlling shareholder of EPCO.

As generally used in the energy industry and in this discussion, the identified terms have the following meanings:

                     /d       = per day
                     BBtus    = billion British thermal units
                     MBPD     = thousand barrels per day
                     MMBbls   = million barrels
                     MMBtus   = million British thermal units
                     Bcf      = billion cubic feet

Cautionary Note Regarding Forward-Looking Statements

This discussion contains various forward-looking statements and information that are based on our beliefs and those of our general partner, as well as assumptions made by us and information currently available to us. When used in this document, words such as "anticipate," "project," "expect," "plan," "seek," "goal," "forecast," "intend," "could," "should," "will," "believe," "may," "potential" and similar expressions and statements regarding our plans and objectives for future operations, are intended to identify forward-looking statements. Although we and our general partner believe that such expectations reflected in such forward-looking statements are reasonable, neither we nor our general partner can give any assurances that such expectations will prove to be correct. Such statements are subject to a variety of risks, uncertainties and assumptions as described in more detail in Item 1A "Risk Factors" included in our Annual Report on Form 10-K for 2008. If one or more of these risks or uncertainties materialize, or if underlying assumptions prove incorrect, our actual results may vary materially from those anticipated, estimated, projected or expected. You should not put undue reliance on any forward-looking statements. The forward-looking statements in this quarterly report speak only as of the date hereof. Except as required by federal and state securities laws, we undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or any other reason.

Critical Accounting Policies and Estimates

A summary of the significant accounting policies we have adopted and followed in the preparation of our financial statements is included in our Annual Report on Form 10-K for the year ended December 31, 2008. Certain of these accounting policies require the use of estimates. As more fully described therein, the following estimates, in our opinion, are subjective in nature, require the exercise of judgment and involve complex analysis: depreciation methods and estimated useful lives of property, plant and equipment; measuring recoverability of long-lived assets and equity method investments; amortization methods and estimated useful lives of qualifying intangible assets; revenue recognition policies and use of estimates for revenues and expenses; and natural gas imbalances. These estimates are based on our current knowledge and understanding and may change as a result of actions we take in the future. Changes in these estimates will occur as a result of the passage of time and the occurrence of future events. Subsequent changes in these estimates may have a significant impact on our financial position, results of operations and cash flows.

Overview of Business

Duncan Energy Partners is a publicly traded Delaware limited partnership, the common units of which are listed on the NYSE under the ticker symbol "DEP." Duncan Energy Partners is engaged in the business of (i) natural gas liquids ("NGL") transportation and fractionation; (ii) the storage of NGL and petrochemical products; (iii) the transportation of petrochemical products; (iv) the gathering, transportation and storage of natural gas; and (v) the marketing of NGLs and natural gas.

We have three reportable business segments: Natural Gas Pipelines & Services; NGL Pipelines & Services; and Petrochemical Services. Our business segments are generally organized and managed according to the type of services rendered (or technologies employed) and products produced and/or sold.

We conduct substantially all of our business through DEP OLP. At March 31, 2009, we were owned 99.3% by our limited partners and 0.7% by DEP GP. At March 31, 2009, EPO owned approximately 74% of our limited partner interests and 100% of our general partner. DEP GP is responsible, as general partner, for managing our business and operations.

Our business purpose is to acquire, own and operate a diversified portfolio of midstream energy assets and to support the growth objectives of EPO and other commonly-controlled affiliates. One of our principal advantages is our relationship with EPO and EPCO. Our assets connect to various midstream energy assets of EPO and form integral links within EPO's value chain of assets. We believe that the operational significance of our assets to EPO, as well as the alignment of our respective economic interests in these assets, will result in a collaborative effort to promote their operational efficiency and maximize value. In addition, we believe our relationship with EPO and EPCO provides us with a distinct benefit in both the operation of our assets and the identification and execution of potential future acquisitions that are not otherwise taken by Enterprise Products Partners or Enterprise GP Holdings in accordance with our business opportunity agreements. See Note 13 of Item 1 of this quarterly report for additional information regarding our relationship with EPO and EPCO.

Basis of Financial Statement Presentation

Effective February 1, 2007, Duncan Energy Partners acquired controlling ownership interests in five midstream energy companies (the "DEP I Midstream Businesses") from EPO in a dropdown transaction. The DEP I Midstream Businesses consist of (i) Mont Belvieu Caverns, LLC ("Mont Belvieu Caverns"); (ii) Acadian Gas, LLC ("Acadian Gas"); (iii) Enterprise Lou-Tex Propylene Pipeline L.P. ("Lou-Tex Propylene"), including its general partner; (iv) Sabine Propylene Pipeline L.P. ("Sabine Propylene"), including its general partner; and (v) South Texas NGL Pipelines, LLC ("South Texas NGL").

On December 8, 2008, Duncan Energy Partners entered into a Purchase and Sale Agreement (the "DEP II Purchase Agreement") with EPO and Enterprise GTM Holdings L.P. ("Enterprise GTM," a wholly owned subsidiary of EPO). Pursuant to the DEP II Purchase Agreement, DEP OLP acquired 100% of the membership interests in Enterprise Holding III, LLC ("Enterprise III") from Enterprise GTM, thereby acquiring a 66% general partner interest in Enterprise GC, L.P. ("Enterprise GC"), a 51% general partner interest in Enterprise Intrastate L.P. ("Enterprise Intrastate") and a 51% membership interest in Enterprise Texas Pipeline LLC ("Enterprise Texas"). Collectively, we refer to Enterprise GC, Enterprise Intrastate and Enterprise Texas as the "DEP II Midstream Businesses." EPO was the sponsor of this second dropdown transaction.

Prior to the dropdown of controlling ownership interests in the DEP I and DEP II Midstream Businesses to Duncan Energy Partners, EPO owned these businesses and directed their respective activities for all periods presented (to the extent such businesses were in existence during such periods). Each of the dropdown transactions was accounted for at EPO's historical costs as a reorganization of entities under common control in a manner similar to a pooling of interests. On a standalone basis, Duncan Energy Partners did not own any assets prior to February 1, 2007.

References to the "former owners" of the DEP I and DEP II Midstream Businesses represent the ownership of EPO in these businesses prior to the effective date of the related dropdown transactions. References to "Duncan Energy Partners" mean the registrant and its consolidated subsidiaries since February 2007. Generic references to "we," "us," and "our" mean the combined and/or consolidated businesses included in these financial statements for each reporting period.

For additional information regarding the dropdowns of the DEP I and DEP II Midstream Businesses, as well as the recast of our historical financial information in connection with the DEP II

dropdown transaction, please read Note 1 of the Notes to Consolidated Financial Statements included under Item 8 of our Annual Report on Form 10-K for the year ended December 31, 2008.

Our results of operations for the three months ended March 31, 2009 are not necessarily indicative of results expected for the full year.

Effective January 1, 2009, we adopted the provisions of Statement of Financial Accounting Standards ("SFAS") 160, Noncontrolling Interests in Consolidated Financial Statements. SFAS 160 established accounting and reporting standards for noncontrolling interests, which were previously identified as Parent interest in our financial statements. This new standard requires, among other things, that (i) noncontrolling interests be presented as a component of equity on our consolidated balance sheet (i.e., elimination of the "mezzanine" presentation previously used for Parent interest); and (ii) elimination of "Parent interest in income of subsidiaries" amounts as a deduction in deriving net income or loss and, as a result, that net income or loss be allocated between our unitholders and general partner on one hand and noncontrolling interests on the other. Earnings per unit amounts are not affected by these changes.

The consolidated financial statements included in this Quarterly Report on Form 10-Q reflect the changes required by SFAS 160. As a result, net income reported for the first quarter of 2008 in these financial statements is higher than that disclosed previously; however, the allocation of such net income results in our unitholders, general partner and Parent (i.e., the noncontrolling interest) receiving the same amounts as they did previously.

Recent Developments

In March 2009, we and Enterprise Products Partners announced that construction has been completed on the 174-mile Sherman Extension expansion of our Texas Intrastate System, which extends through the heart of the prolific Barnett Shale natural gas play of North Texas. The completion of the Sherman Extension adds
1.1 Bcf/d of incremental natural gas takeaway capacity from the region, while providing producers in the Barnett Shale, and as far away as the Waha area of West Texas, with greater flexibility to reach the most attractive natural gas markets. The Texas Intrastate System is part of our Natural Gas Pipelines & Services business segment.

Results of Operations

We have three reportable business segments: Natural Gas Pipelines & Services; NGL Pipelines & Services; and Petrochemical Services. Our business segments are generally organized and managed according to the type of services rendered (or technologies employed) and products produced and/or sold.

We evaluate segment performance based on the non-GAAP financial measure of gross operating margin. Gross operating margin (either in total or by individual segment) is an important performance measure of the core profitability of our operations. This measure forms the basis of our internal financial reporting and is used by management in deciding how to allocate capital resources among business segments. We believe that investors benefit from having access to the same financial measures that our management uses in evaluating segment results. The GAAP financial measure most directly comparable to total segment gross operating margin is operating income. Our non-GAAP financial measure of total segment gross operating margin should not be considered as an alternative to GAAP operating income.

Selected Volumetric Data

The following table presents average throughput and fractionation volumes for
our principal pipelines and facilities. These statistics are presented in total
for each asset (or asset group) irrespective of ownership interest (i.e., on a
100% basis), with the exception of pipeline throughput volumes for Evangeline (a
component of the Acadian Gas System). We report volumes for Evangeline on a net
basis to our ownership interest.

                                                                         For the Three Months
                                                                            Ended March 31,
                                                                     2009                     2008
Natural Gas Pipelines & Services, net:
  Natural gas throughput volumes (BBtus/d)
   Texas Intrastate System                                               4,418                   3,801
   Acadian Gas System:
     Transportation volumes                                                383                     410
     Sales volumes (1)                                                     288                     300
   Total natural gas throughput volumes                                  5,089                   4,511
NGL Pipelines & Services, net:
  NGL throughput volumes (MBPD)
    South Texas NGL System - Pipelines                                     115                     137
  NGL fractionation volumes (MBPD)
    South Texas NGL System - Fractionators                                  79                      82
Petrochemical Services, net:
  Propylene throughput volumes (MBPD)
   Lou-Tex Propylene Pipeline                                               13                      30
   Sabine Propylene Pipeline                                                 9                      10
   Total propylene throughput volumes                                       22                      40

(1) Includes average net sales volumes for Evangeline of 35.0 BBtus/d and 36.7 BBtus/d for the three months ended March 31, 2009 and 2008, respectively.

Comparison of Results of Operations

The following table summarizes the key components of our results of operations
for the periods indicated (dollars in millions):

                                                                  For the Three Months
                                                                     Ended March 31,
                                                                  2009             2008
Revenues                                                       $     256.8       $   363.6
Operating costs and expenses                                         239.4           337.5
General and administrative costs                                       2.8             5.2
Equity in income of Evangeline                                         0.2             0.2
Operating income                                                      14.8            21.1
Interest expense                                                      (3.8 )          (2.8 )
Net loss (income) attributable to noncontrolling interest:
  DEP I Midstream Businesses - Parent                                 (1.6 )          (5.6 )
  DEP II Midstream Businesses - Parent                                10.5              --
Net income attributable to Duncan Energy Partners L.P.                19.9            13.3

For information regarding noncontrolling interest, see the section titled "Earnings attributable to Noncontrolling Interest" within this Item 2.

Our gross operating margin by business segment and in total is as follows for the periods indicated (dollars in millions):

                                                     For the Three Months
                                                        Ended March 31,
                                                     2009             2008
         Natural Gas Pipelines & Services         $     38.8       $     40.8
         NGL Pipelines & Services                       20.8             22.7
         Petrochemical Services                          2.5              2.9
           Total segment gross operating margin   $     62.1       $     66.4

For a reconciliation of non-GAAP gross operating margin to GAAP operating income and further to GAAP net income, see "Other Items - Non-GAAP Reconciliations" within this Item 2. For additional information regarding our business segments, see Note 12 of the Notes to Unaudited Condensed Consolidated Financial Statements included under Item 1 of this quarterly report.

The following table summarizes the contribution to revenues from each business segment (including the effects of eliminations and adjustments) during the periods indicated (dollars in millions):

                                                      For the Three Months
                                                         Ended March 31,
                                                       2009            2008
        Natural Gas Pipelines & Services:
         Sales of natural gas                       $     124.9       $ 229.2
         Natural gas transportation services               75.2          74.4
         Natural gas storage services                       2.5           1.3
           Total segment revenues                   $     202.6       $ 304.9

        NGL Pipelines & Services:
         Sales of NGLs                              $       6.2       $  11.6
           Sales of other products                          3.8           3.3
           NGL and petrochemical storage services          24.1          19.4
         NGL fractionation services                         7.4           7.8
           NGL transportation services                      8.7          12.1
           Other services                                   0.6           0.7
           Total segment revenues                   $      50.8       $  54.9

        Petrochemical Services:
         Propylene transportation services          $       3.4       $   3.8

        Total consolidated revenues                 $     256.8       $ 363.6

Comparison of the Three Months Ended March 31, 2009 with the Three Months Ended March 31, 2008

Revenues for the first quarter of 2009 were $256.8 million compared to $363.6 million for the first quarter of 2008. The $106.8 million quarter-to-quarter decrease in consolidated revenues is primarily due to lower energy commodity sales volumes and prices during the first quarter of 2009 relative to the first quarter of 2008. These factors accounted for a $109.2 million quarter-to-quarter decrease in consolidated revenues from our marketing activities largely due to lower natural gas prices during the first quarter of 2009 relative to the first quarter of 2008. Revenues from our natural gas pipeline and storage businesses increased $2.0 million quarter-to-quarter attributable to higher pipeline transportation volumes and fees and increased storage activity. Collectively, revenues from NGL fractionation, transportation and storage services increased $0.8 million quarter-to-quarter primarily due to higher NGL storage volumes and fees during the first quarter of 2009 relative to the first quarter of 2008. Revenues from propylene transportation decreased $0.4 million quarter-to-quarter due to lower transportation volumes.

Operating costs and expenses were $239.4 million for the first quarter of 2009 versus $337.5 million for the first quarter of 2008. The $98.1 million quarter-to-quarter decrease in consolidated operating costs and expenses is primarily due to lower cost of sales associated with our natural gas and

NGL marketing activities. The cost of sales of our natural gas and NGL products decreased $103.9 million quarter-to-quarter as a result of lower volumes and energy commodity prices. Collectively, the remainder of our consolidated operating costs and expenses increased $5.8 million primarily due to higher operating costs and expenses at our Mont Belvieu Storage complex and depreciation expense we recorded during the first quarter of 2009 for the recently completed Sherman Extension of our Texas Intrastate System.

These changes in our revenues and operating costs and expenses quarter-to-quarter are explained primarily by changes in energy commodity prices. The market price of natural gas (as measured at Henry Hub) decreased 39% to an average of $4.91 per MMBtu during the first quarter of 2009 versus an average of $8.03 per MMBtu during the first quarter of 2008. The weighted-average indicative market price for NGLs was $0.66 per gallon during the first quarter of 2009 versus $1.49 per gallon during the first quarter of 2008 - a 56% decrease quarter-to-quarter. Our determination of the weighted-average indicative market price for NGLs is based on U.S. Gulf Coast prices for such products at Mont Belvieu, Texas, which is the primary industry hub for domestic NGL production.

General and administrative costs were $2.8 million for the first quarter of 2009 compared to $5.2 million for the first quarter of 2008. The $2.4 million quarter-to-quarter decrease in general and administrative costs is primarily due to lower costs associated with the DEP II Midstream Businesses.

Operating income for the first quarter of 2009 was $14.8 million compared to $21.1 million for the first quarter of 2008. Consolidated revenues and certain operating costs and expenses can fluctuate significantly due to changes in energy commodity prices (e.g., the price of natural gas and NGLs) without significantly affecting our operating income. Consequently, the aforementioned changes in revenues and costs and expenses contributed to the $6.3 million quarter-to-quarter decrease in operating income.

Interest expense increased $1.0 million quarter-to-quarter primarily due to borrowings we made in connection with the DEP II dropdown transaction in December 2008. Provision for income taxes increased $0.6 million quarter-to-quarter primarily due to an increase in expenses attributable to the Texas Margin Tax.

As a result of items noted in the previous paragraphs, net income decreased $7.9 million quarter-to-quarter to $11.0 million for the first quarter of 2009 compared to $18.9 million for the first quarter of 2008.

Net income attributable to noncontrolling interests reflects an $8.9 million allocation of net losses for the first quarter of 2009 versus an earnings allocation of $5.6 million for the first quarter of 2008. For information regarding our noncontrolling interest amounts, see "Earnings Attributable to Noncontrolling Interest in Subsidiaries" within this Item 2. Net income attributable to Duncan Energy Partners increased $6.6 million quarter-to-quarter to $19.9 million for the first quarter of 2009 compared to $13.3 million for the first quarter of 2008. Net income attributable to Duncan Energy Partners for the first quarter of 2008 includes $7.3 million of income allocated to former owners of the DEP II Midstream Businesses.

The following information highlights significant quarter-to-quarter variances in gross operating margin by business segment:

Natural Gas Pipelines & Services. Gross operating margin from this business segment was $38.8 million for the first quarter of 2009 compared to $40.8 million for the first quarter of 2008, a $2.0 million quarter-to-quarter decrease. Total natural gas throughput volumes were 5,089 BBtus/d for the first quarter of 2009 compared to 4,511 BBtus/d for the first quarter of 2008. Gross operating margin from our Acadian Gas System decreased $3.4 million quarter-to-quarter primarily due to lower sales margins during the first quarter of 2009 relative to the first quarter of 2008. Gross operating margin from our Texas Intrastate System increased $0.3 million quarter-to-quarter attributable to a 617 BBtus/d quarter-to-quarter increase in natural gas throughput volumes and higher transportation and fees, the effects of which were partially offset by higher ad valorem tax and pipeline integrity expenses. Collectively, results for the Texas Intrastate and Acadian Gas Systems include $0.4 million of additional property damage repair expenses during the first quarter of 2009 resulting from Hurricanes Gustav and Ike.

. . .