This book examines the knowledge and therapeutic use of opium and various species of poppy by physicians in ninth-century Baghdad (the leading medical centre then) as seen in key works by six outstanding physicians, with reference to others. The study opens with a brief look at early Islamic knowledge of the Graeco-Roman use of opium, while examining in detail entries on opium and poppy in the Arabic version of Dioscorides's influential and fundamental Materia medica. The core of the study aims to establish to what extent and how opium and poppy are used in the selected books of the six physicians.The comprehensive glossaries of Materia medica, Ailments and Conditions, and General Terms are particularly useful for the medical historian.