The fundamental clinical features of PCOS include hirsutism and menstrual irregularities from the time of menarche. Obesity is present in approximately 50% of these patients, some of whom also carry a diagnosis of NIDDM. The biochemical abnormalities associated with the clinical picture include LH hypersecretion, hyperandrogenism, acyclic estrogen production, subnormal SHBG levels, and hyperinsulinemia. Hirsutism usually progresses slowly in patients with PCOS; however, the clinical presentation can resemble virilizing tumors, late-onset CAH, or Cushing syndrome. Virilization or rapidly progressive hirsutism requires immediate investigation to rule out a virilizing tumor. Goals of therapy for teenage patients include decreasing levels of bioavailable androgen, blockade of androgen action at target tissues, stabilization of the endometrium, and reduction of insulin resistance. Although the original description of PCOS by Stein and Leventhal was published in 1935, the cause of PCOS remains unknown. This reason, coupled with the fact that PCOS-related insulin resistance is an important cause of NIDDM in women, has caused this disorder to become one of interest and active investigation. Future research will likely be able to delineate mechanisms behind the defects of carbohydrate metabolism and ascertain large multigeneration kindreds for linkage analyses to identify affected genes. Future studies are also likely to confirm whether young women with PCOS are at increased risk for cardiovascular disease and other long-term health complications. As new pathophysiologic mechanisms are identified, the promise of new therapies arises, including treatments that could potentially reduce the long-term incidence of adverse health consequences.