Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenic chronic anovulation and is the most common endocrinopathy among reproductive- age women. The syndrome is not to be confused with the presence of polycystic ovaries (PCO), which has a varied etiology and is not specific to the syndrome. PCOS is associated with significant insulin resistance as well as with defects in insulin secretion. A defect in insulin mediated receptor autophosphorylation has been found in a substantial proportion of PCOS women. This defect is unique to PCOS and is not found in other common states of insulin resistance. These abnormalities, combined with obesity, predispose PCOS women to developing non-insulin dependent diabetes mellitus. Another long-term sequelae that may be related to insulin resistance is cardiovascular disease. There is unfortunately no readily available clinical test at present to diagnose insulin resistance in PCOS women. Treatment considerations for improving insulin sensitivity in PCOS women should focus on weight loss regimens and the avoidance of interventions that worsen insulin sensitivity. The initial investigational use of insulin-sensitizing agents in these women has shown favorable responses.