Islam requires every Muslim who is physically and financially able to make the journey to the holy city of Mecca at least once in his or her life.
The height of Hajj corresponds with the major Islamic holy day Eid al-Adha, which commemorates Abraham's readiness to sacrifice his son on Divine orders.
The pilgrimage, conducted over five days, includes numerous detailed rituals including wearing a special garment that symbolizes human equality and unity before God, a circular, counter-clockwise procession around the Kaaba, and the symbolic stoning of evil.
Kaaba (Ka'bah), a cube-shaped structure draped in black silk, is the most sacred shrine of Islam and the chief goal of the pilgrimage.
There is a black stone enclosed in a silver ring in the eastern corner of the Kaaba. Muslims believe that the stone was given to Abraham by the angel Gabriel. Participants touch or kiss the stone to end the ceremony around the Kaaba.
People who have completed the pilgrimage may add the phrase al-Hajj or hajji (pilgrim) to their names.
1987 - More than 400 people, mainly Iranian Shiite pilgrims, are killed in clashes with Saudi security forces during anti-Western protests in Mecca.
1990 - 1,426 pilgrims are trampled to death.
1994 - A stampede near Jamarat Bridge kills 270 pilgrims.
1998 - One hundred eighty people die in a stampede near Mecca at the end of Hajj.
January 5, 2006 - A small hotel in Mecca collapses, killing at least 76 people. The hotel, Luluat Alkheir, is occupied by Asian pilgrims when it collapses.
January 12, 2006 - A stampede kills at least 363 people. The stampede, like others in the past, happens during the stone-throwing ritual in which the pilgrims stone a symbolic devil.