ZIONS BANCORPORATION

On April 27, 2010, Zions Bancorporation increased the Auction Amount of its 4.00% Senior Medium-Term Notes due May 6, 2011 (the “Notes”) offered by the Preliminary Terms and Conditions dated April 20, 2010 from $1,250,000 to $2,000,000. The auction will end as scheduled at 2:00 p.m. ET, Monday, May 3, 2010, subject to the 2-Minute Rule referenced in the Prospectus.

The Notes are not savings accounts, deposits or other obligations of any of the issuer’s banks or non-bank subsidiaries and are not insured by the Federal Deposit Insurance Corporation, the Board of Governors of the Federal Reserve System or any other government agency. The Notes are not guaranteed under the Federal Deposit Insurance Corporation’s Temporary Liquidity Guarantee Program.

Zions Bancorporation has filed a registration statement (Registration Statement No. 333-158319, including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus dated March 31, 2009 contained in that registration statement, the prospectus supplement dated April 21, 2009, the prospectus supplement dated September 14, 2009 and other documents Zions Bancorporation has filed with the SEC for more complete information about Zions Bancorporation and this offering. You may get these documents and other documents Zions Bancorporation has filed for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, Zions Bancorporation or a representative will arrange to send you the prospectus and other documents Zions Bancorporation has filed with the SEC if you request it by calling toll free (800) 524-8875.