The major causal theories of and treatment approaches to male and female homosexuality are critically reviewed. Neither biological, psychoanalytic, nor learning and social-learning theories are found to provide convincing evidence for the etiology of homosexuality. All of these accounts, however, are viewed as providing mixed empirical support for their predictions, with social-learning research presenting the most consistent evidence. It is argued that both social-learning research findings and results from retrospective studies suggest that homosexuality may best be linked to the early qualitative learning and development of one's gender identity and gender role. Both psychoanalytic therapy and behavior therapy are found to have minimal successes and many failures. Most therapeutic successes seem to be with bisexuals rather than with exclusive homosexuals. The combined use of psychotherapy and specific behavioral techniques is seen to offer some promise for heterosexual adaptation with certain kinds of patients. However, it is argued that better prospects for intervention in homosexuality lie in its prevention through the early identification and treatment of the potential homosexual child.