Great strides have been made in the last ten years in the immunology and chemotherapy of leprosy which have altered concepts of epidemiology and control. Animal models of leprosy have added materially to knowledge of the transmission of leprosy. There is also a better understanding of the physical and psychological disabilities endured by leprosy patients. The stigma of the disease however, remains fully entrenched in many parts of the world, and still separates patients with leprosy from their fellow men. This work sets out to provide a basic knowledge and explanation of leprosy for students in developing countries and for doctors and scientists elsewhere, who want an introduction to the disease and the problems it continues to pose. Five chapters of this edition have been extensively revised, and a new chapter added on mycobacterium laprae itself.