Polycystic ovary syndrome (PCOS), also referred to as Stein-Leventhal syndrome, is one of the most common endocrinopathies. It is characterized by hyperandrogenism, hyperinsulinemia, central obesity, polycystic ovaries, and anovulation. However, some of these manifestations, including the polycystic ovaries, are neither specific for the disorder, nor found in all affected individuals. PCOS appears to be due to one or more primary defects in the upstream gonadotropin/androgen and/or insulin pathway, with the polycystic ovaries being one of many downstream manifestations. Yet, the pathophysiology of PCOS is not completely elucidated. Since the primary defect underlying PCOS may be an upstream endocrine and/or metabolic disturbance, rather than a defect in the ovaries themselves, we hypothesize that this aberration can also arise in men and that the absence of polycystic ovaries in men with other stigmata of the disorder should not eliminate the diagnosis. Our hypothesis is supported by the observation that a genetic susceptibility to PCOS exists, and that PCOS-type manifestations are not limited to women. Indeed, male relatives may suffer from insulin resistance, obesity, diabetes mellitus, and cardiovascular disease. Therefore, recognition of this syndrome in men is important, since pharmacologic treatments identified for women with PCOS may alleviate metabolic problems related to insulin resistance and its sequelae in men with a similar underlying defect. We suggest that first-degree relatives of patients with PCOS should be examined not only for phenotypic features characteristic of PCOS but also for biochemical evidence of hyperinsulinemia and hyperandrogenism. In addition to examining these individuals for obesity, the women should be evaluated for hirsutism and the men should be screened for early-onset male-pattern alopecia and excess hairiness. Serologic evaluation should included the ratio of fasting levels of glucose to insulin, a glucose tolerance test, the free testosterone level and the sex hormone-binding globulin level. Finally, both male and female first-degree relatives of patients with PCOS should be tested for the underlying molecular defect(s) of this condition, once it is identified. As new treatments for PCOS emerge, e.g. insulin-sensitizing drugs, it will be important to determine if these treatments have beneficial effects on the metabolic symptoms and complications in all afflicted patients, regardless of gender.