Theoretical writings and research suggest that the onset, course, treatment, and prevention of mental disorders among lesbians and gay men differ in important ways from those of other individuals. Recent improvements in studies of sexual orientation and mental health morbidity have enabled researchers to find some elevated risk for stress-sensitive disorders that is generally attributed to the harmful effects of antihomosexual bias. Lesbians and gay men who seek mental health services must find culturally competent care within systems that may not fully address their concerns. The affirmative therapies offer a model for intervention, but their efficacy and effectiveness need to be empirically documented. Although methodological obstacles are substantial, failure to consider research questions in this domain overlooks the welfare of individuals who may represent a sizable minority of those accessing mental health services annually.