The effects of alcohol and drugs on sexual function are important to consider in clinical histories and medication prescribing practices. Virtually all aspects of the human sexual response are affected by alcohol and drugs: 1. Desire (libido) is reduced. 2. Performance. Impotency as defined by lack of erection and ejaculation occurs. 3. Dissatisfaction ensues. These effects of alcohol and drugs can be understood and illustrated by examining the phases of excitement, plateau, orgasm, and resolution in the human sexual response. The important first step in the treatment of sexual dysfunction is to identify the alcohol/drug/medication use. The next is to recognize the profound effect it can have on the human sexual response. Furthermore, knowledge of the mechanism of action of the drugs and a basic conception of the physiology and psychology of sexual performance are necessary to predict the course of the sexual dysfunction. In many instances, the sexual dysfunction is reversible even after chronic alcohol/drug/medication use.