This book deals with the spirit possession phenomenon in relation to biomedical practices in Zanzibar Town, on Zanzibar islands, Tanzania. The possession phenomenon is explored from the perspective of therapeutic option and as a form of cultural knowledge. It is argued that the popularity of possession healing and the work of spirit healers can be understood only in relation to the history of biomedical interventions and the present state of biomedical institutions in Zanzibar. This exploration of health and healing in an urban Islamic context, off the coast of East Africa, is based on ethnographic fieldwork and archive work.