On November 26, 2008, United Therapeutics Corporation (the "Company") commenced an exchange offer with respect to certain outstanding options to purchase shares of the Company's common stock that have an exercise price per share greater than $65.00 (the "Offer"). The Company has filed with the Securities and Exchange Commission (the "Commission") a Schedule TO containing the terms and conditions of the Offer. The Offer expired at 5:00 p.m., New York City time, on Friday, December 26, 2008. The Company reported the results of the Offer in an amendment to its Schedule TO filed with the Commission on December 31, 2008.

Options were exchanged in the Offer by the Company's executive officers as follows:

Dr. Martine Rothblatt, the Company's Chairman and Chief Executive Officer, exchanged options to purchase 582,607 shares of the Company's common stock, out of an aggregate 909,434 shares subject to options held by Dr. Rothblatt that were eligible for exchange.

Dr. Roger Jeffs, the Company's President and Chief Operating Officer, exchanged options to purchase 167,125 shares of the Company's common stock, representing all of his options eligible for exchange.

Mr. Paul Mahon, the Company's Executive Vice President, Strategic Planning and General Counsel, exchanged options to purchase 144,475 shares of the Company's common stock, representing all of his options eligible for exchange.

These option exchanges have been reported by the executive officers on Forms 4 filed on December 30, 2008.

All of the replacement options were issued on December 26, 2008, and have an exercise price of $61.50 per share, representing the closing price of the Company's common stock, as reported on the NASDAQ Global Select Market, on December 26, 2008. Any replacement options granted in exchange for vested options are subject to a one-year vesting schedule. Any replacement options granted in exchange for unvested options are subject to the vesting schedule of the original unvested options. All replacement options were granted under the Company's Amended and Restated Equity Incentive Plan and, other than the changes described herein, have terms and conditions identical to those contained in the corresponding original option grants.

(d) Exhibits

Exhibit No.                           Description of Exhibit
99.1           United Therapeutics Corporation Notice of Grant, incorporated by
               reference to Exhibit (d)(4) of the Company's Tender Offer Statement
               filed on Schedule TO on November 26, 2008.