press release

Unocal completes partial redemption of trust convertible preferred securities

El Segundo, Calif., Sept. 21, 2004 - Unocal Corporation (NYSE: UCL) today said it has completed its previously announced redemption of approximately one-half of Unocal's outstanding 6-1/4% Trust Convertible Preferred Securities.

Unocal redeemed 4.9 million shares of the preferred securities with an aggregate liquidation value of $246 million. Including the 1.25-percent redemption premium and unpaid distributions, the total cost of the redemption program was $250 million. An additional 304,150 preferred shares that were called for redemption were converted by the holders to Unocal common stock.

The partial redemption eliminated the potential dilution of 5.8 million common shares (based on the conversion rate to common stock for the preferred securities). The redemption program is expected to reduce Unocal's book debt by nearly $269 million and cut the company's annual interest expense by about $16 million.

The convertible preferred redemption was one aspect of a three-part, $500 million cash expenditure program that Unocal announced in July 2004. The other aspects, which have already been completed, included a $100 million voluntary contribution to Unocal's U.S. pension plan and the repurchase of $150 million of Unocal's common stock.

The common stock repurchase and preferred redemption programs reduced Unocal's diluted share count by about 10 million shares, or nearly 4 percent of the diluted share balance as of June 30, 2004.

The total cash outlay for the three programs represented approximately one-half of the cash balance that Unocal reported at the end of the second quarter 2004. Unocal has said that if commodity prices remain high and the company has additional excess cash on hand at year-end, it may consider expanding one or more of these cash expenditure programs.

About Unocal Corporation

Unocal is one of the world's leading independent natural gas and crude oil exploration and production companies with principal operations in North America and Asia.

This news release contains forward-looking statements about matters such as expected impacts of the redemption on Unocal's debt and interest expense and potential uses of available cash. Although these statements are based upon Unocal's current expectations and beliefs, they are subject to known and unknown risks and uncertainties that could cause actual results and outcomes to differ materially from those described in, or implied by, the forward-looking statements, including market conditions for Unocal's securities, volatility in commodity prices and the effectiveness of Unocal's hedging program; the extent of Unocal's operating cash flow and other capital resources available to fund its capital expenditures; and other risks and uncertainties discussed in Unocal's 2003 Annual Report on Form 10-K, as amended, and subsequent reports filed by Unocal with the Securities and Exchange Commission (SEC File No. 1-8483). Copies of Unocal's SEC filings are available from Unocal by calling 800-252-2233 or from the SEC by calling 800-SEC-0330. The reports are also available on the Unocal web site. Unocal undertakes no obligation to update the forward-looking statements in this news release to reflect future events or circumstances. All such statements are expressly qualified by this cautionary statement.

Updated: September 2004