This is the first social history of the descendants of the Prophet Muhammad in early Islam. The 'Alids are the descendants of the Prophet Muhammad, the elite family of Islam. The respect and veneration they are accorded is unparalleled in Islamic society, regardless of political or religious affiliation. They have played a major role in Islamic history: famous early rebels and founders of major Islamic sects, and many rulers - such as the 10th century Fatimids in Egypt, the current kings of Jordan and Morocco, Ayatollah Khomeini and the Aga Khan - all claimed 'Alid descent. This first in-depth study of the 'Alids focuses on the crucial formative period from the Abbasid Revolution to the Saljuq period, 750-1100. Exploring the rise of the 'Alids as a social phenomenon, the author asks how this family attained and extended its status over the centuries. It covers the crucial formative period from the Abbasid Revolution of 750 to the Seljuq period of 1100. It opens up new possibilities for understanding the sectarian differences between Sunnis and Shi'ites through an in-depth exploration of the distinction between Shi'ites and 'Alids. It draws on historical, legal and biographical material, recent genealogical works and a wide range of primary sources in both Arabic and Persian.