Human sexual behaviour is determined by different regulatory systems. Central and peripheral nervous system, endocrine and vascular systems, all play a pivotal role in the modulation of male sexual activity. Therefore, many steps of possible drug interference can be recognized. In this regard, drugs are usually classified on the basis of their side effects (impairment of libido, erection and/or ejaculation). In the present work we review the sexual-related side effects of drugs of widespread clinical use on the basis of their mechanism and site of action.