Research is reviewed on diagnostic and treatment procedures for erectile dysfunction. Both physical and psychological assessment procedures are discussed, emphasizing the need to rely on prognosis rather than differential diagnosis in treatment formulations. Outcome is reviewed for physical treatments, including implants, papaverine injections, and vacuum constriction devices. Outcome research for psychological interventions published since 1974 is reviewed. Methodological problems are highlighted, including the need for controlled clinical trials, problems in the control of therapist variables, measurement problems, the need for increased treatment specificity, the need to explore prognostic indicators, the use and reporting of statistics, comparability across studies, maintenance issues, and the need for improved follow-up.