This report contains the collective views of an international group of experts on the epidemiology, control, treatment, classification and immunology of leprosy. The disadvantages of compulsory isolation are stressed and the superior effectiveness of sulfone treatment over all others in nontoxic doses is emphasized. The infectivity of open and closed cases and the basic principles of control are discussed. There are many problems still to be solved and this succinct report brings us up to date on the various aspects of a disease still of great importance in many parts of the world.