In 1990 Green and Fleming concluded that sex reassignment surgery (SRS) is an effective treatment for transsexuality because it reduced gender dysphoria drastically. Since 1990, many new outcome studies have been published, raising the question as to whether the conclusion of Green and Fleming still holds. After decribing terminological and conceptual developments related to the treatment of gender identity disorder (GID), follow-up studies, including both adults and adolescents, of the outcomes of SRS are reviewed. Special attention is paid to the effects of SRS on gender dysphoria, sexuality, and regret. Despite methodological shortcomings of many of the studies, we conclude that SRS is an effective treatment for transsexualism and the only treatment that has been evaluated empirically with large clinical case series.