A 3-year study of male prostitutes is presented with relevant data about their origin, their social and family background, education, sexuality, drug and alcohol use, and delinquency. A classification has been developed which separates the male prostitutes into four groups: group I, Full-time street and bar hustlers; II, full-time call boys or kept boys; group III, part-time hustlers, usually students or employed; and group IV peer-delinquents, who use prostitution and homosexuality as an extension of other delinquent acts [assault and robbery]. Similarities and differences between the four groups in terms of their psychosocial background, motives, and type of operation are described. Limited follow-up data indicate that only part-time male prostitutes, who continue in education or vocational training, have a reasonable expectation of an eventually stable social adjustment.