In addition to the seven principal tenets of faith, there are also traditional religious practices that are intimately associated with Shia Islam. These include the observance of the month of martyrdom, Moharram, and pilgrimages to the shrines of the Twelve Imams and their various descendants. The Moharram observances commemorate the death of the Third Imam, Husayn, who was the son of Ali and Fatima and the grandson of Muhammad. He was killed near Karbala in modern Iraq in A.D. 680 during a battle with troops supporting the Umayyad caliph. Husayn's death is commemorated by Shias with passion plays and is an intensely religious time.

Pilgrimage to the shrines of Imams is a specific Shia custom. The most important shrines in Iran are those for the Eighth Imam in Mashhad and for his sister Fatima in Qom. There are also important secondary shrines for other relatives of the Eighth Iman in Rey, adjacent to south Tehran, and in Shiraz. In virtually all towns and in many villages there are numerous lesser shrines, known as imamzadehs, which commemorate descendants of the imams who are reputed to have led saintly lives. Shia pilgrims visit these sites because they believe that the imams and their relatives have power to intercede with God on behalf of petitioners. The shrines in Iraq at Karbala and An Najaf are also revered by Shias.

Data as of December 1987