Here's a look at the life of al Qaeda leader Ayman al-Zawahiri.
Personal: Birth date: June 19, 1951
Birth place: Egypt
Birth name: Ayman Muhammad Rabi al-Zawahiri
Father: Rabie al-Zawahiri, professor of pharmacology
Education: Cairo University medical school, 1974; master's degree in surgery, 1978
Other Facts: Acted as Osama bin Laden's personal physician.
Al-Zawahiri comes from a distinguished Egyptian family. His grandfather, Rabia'a al-Zawahiri, was an Iman at al-Azhar in Cairo. His great-uncle, Abdel-Rahman Azzam, was the first secretary of the Arab League.
The US State Department is offering a reward of up to $25 million for information leading directly to the capture of al-Zawahiri.
Believed by investigators to have played an important role in the September 11th attacks.
Timeline: 1970s - Al-Zawahiri and the Egyptian Islamic Jihad work to overthrow Egyptian President Anwar Sadat and establish an Islamic state.
1980s - Joins the Mujahedeen who are fighting Soviet forces occupying Afghanistan.
1981 - Egyptian President Anwar Sadat is assassinated and al-Zawahiri is arrested. He is convicted on weapons charges, but not for being part of the assassination plot, and sentenced to three years in prison.
1987 - Al-Zawahiri and Osama bin Laden meet.
August 6, 1998 - A fax from al-Zawahiri's group is sent to an Egyptian newspaper saying that the Islamic Jihad is seeking revenge against the US for the arrest of several of its members.
August 7, 1998 - Suicide bombers attack the US embassies in Kenya and Tanzania.
1998 - The Egyptian Islamic Jihad and al Qaeda merge. Al-Zawahiri and bin Laden announce the formation of the World Islamic Front for the Jihad against the Jews and the Crusaders.
June 1999 - Al-Zawahiri is indicted, along with Osama Bin Laden, by the US for the 1998 US Embassy bombings in Kenya and Tanzania.
1999 - Receives a death sentence, in absentia, from an Egyptian court, for an alleged plot to bomb the US embassy in Albania.
December 2001 - Al-Zawahiri's wife and three of his children are killed in a US attack on the family's residence in Afghanistan.
January 13, 2006 - A CIA-led missile strike in Damadola, Pakistan, targets al-Zawahiri, but kills at least 18 other people.
June 8, 2011 - A video of al-Zawahiri eulogizing Osama bin Laden is released.