This book is the first major study in English of a group of late twelfth-century religious enthusiasts, the early Humiliati, who were condemned by the Church as heretics in 1184 but—in a remarkable transition—were reconciled seventeen years later and went on to establish a highly successful religious order in northern Italy. Using a wide range of sources, the nature of the early movement and its processes of institutional development are reconstructed. The book also includes a Bullarium Humiliatorum, a list of papal and episcopal letters and privileges.