Timeline: 1978 - Shah Mohammed Reza Pahlavi's authoritarian rule sparks demonstrations and riots.
January 16, 1979 - The Shah flees Iran and goes to Egypt.
February 1, 1979 - Ayatollah Ruhollah Khomeini returns to Iran after 14 years in exile, to lead the country.
October 22, 1979 - The Shah is allowed to enter the United States to receive medical treatment for cancer.
November 4, 1979 - Iranian students demonstrating outside of the U.S. embassy in Tehran storm the embassy and take 90 people hostage including 66 Americans. The students demand the extradition of the Shah from the United States. Ayatollah Khomeini issues a statement of support for the students' actions.
November 5, 1979 - The Iranian government cancels military treaties with the U.S. and the Soviet Union, treaties that would permit U.S. or Soviet military intervention.
November 6, 1979 - Premier Mehdi Bazargan and his government resign, leaving Ayatollah Khomeini and the Revolutionary Council in power.
November 7, 1979 - President Jimmy Carter sends former Attorney General Ramsey Clark and Senate Intelligence Committee staff director William Miller to Iran to negotiate the release of the hostages. Ayatollah Khomeini refuses to meet with them.
November 14, 1979 - President Carter orders Iranian assets in U.S. banks frozen.
November 17, 1979 - Khomeini orders the release of female and African-American hostages. They are released November 19 and 20, bringing the total number of U.S. hostages to 53.
December 4, 1979 - The United Nations Security Council passes a resolution calling for Iran to release the hostages.
December 15, 1979 - The Shah leaves the United States for Panama.
January 28, 1980 - Six American embassy employees, who avoided capture and hid in the homes of Canadian Embassy officers, flee Iran. In 1997 it is revealed that, along with the Canadian government, the CIA made the escape possible.
March 1980 - The Shah returns to Egypt.
April 7, 1980 - President Carter cuts diplomatic ties with Iran, announcing further sanctions and ordering all Iranian diplomats to leave the United States.
April 25, 1980 - Eight U.S. servicemen are killed when a helicopter and a transport plane collide during a failed attempt to rescue the hostages.
July 11, 1980 - Another hostage is released due to illness. The total number of U.S. hostages is now 52.
July 27, 1980 - The Shah dies of cancer in Egypt.
September 12, 1980 - Ayatollah Khomeini sets new terms for the hostages' release, including the return of the late Shah's wealth and the unfreezing of Iranian assets.
November 1980-January 1981 - Deputy Secretary of State Warren Christopher and his delegation work through mediators in Algeria to negotiate the release of the hostages.
January 19, 1981 - The United States and Iran sign an agreement to release the hostages and unfreeze Iranian assets.
January 20, 1981 - The remaining 52 U.S. hostages are released and flown to Wiesbaden Air Base in Germany.