Anabolic steroids are used therapeutically for various disorders and as ergogenic aids by athletes to augment strength, muscular development, and to enhance performance. There is a wide range of concomitant temporary and permanent adverse effects with steroid administration. Several well-documented adverse actions of these hormones may develop rapidly within several weeks or less (. altered reproductive function) or require up to several years of steroid intake (. liver carcinoma). More recent studies indicate that glucose intolerance, insulin resistance, increased cardiovascular disease risk profiles, cerebral dangers, musculoskeletal injuries, prostate cancer, psychosis and schizophrenic episodes, among others, accompany anabolic steroid intake. There is, at present, no evidence to support the claim that athletes are less susceptible to adverse effects than those individuals receiving hormone treatment in a clinical setting. Based on the available information which has accumulated primarily from cross-sectional, short term longitudinal, and case studies, there is a need: (a) to develop a comprehensive battery of specific and sensitive markers of adverse effects, particularly those that would be able to detect the onset of adverse actions; and (b) to conduct controlled long term longitudinal studies in order to fully understand the extensiveness and mechanisms involved in the occurrence of adverse effects.