From highland peasant farmers in Central Asia to Canadian industrialists, South Asian buisinessmen and Europe-based scholars, the Nizari Ismailis are one of the Muslim world's most diverse Shi'a communities. With adherents living in more than twenty-five countries in Central Asia, South Asia, the Middle East, Europe and North America, they embrace peoples of widely different ethnic and linguistic backgrounds. The spiritual leadership of this highly dynamic community has in recent generations come to be known as the 'Aga Khan'.This book, which coincides with the fiftieth anniversary of the present Aga Khan's succession as Imam, or spiritual leader, of the Ismailis, assesses the achievements of his 'Imamat' in modernising the communities' institutions and creating one of the world's leading development agencies, the Aga Khan Development Network. In the process the book explores how the present Harvard-educated Aga Khan has attempted to preserve and build on a religious tradition rooted in medieval theology while at the same time embracing the modern world without loss of faith or cultural identity.