Homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, exert cytotoxic effects on vascular endothelium. Molecular mechanisms of homocysteine-induced cellular dysfunction include increased inflammatory cytokine expression, altered nitric oxide bioavailability, induction of oxidative stress, activation of apoptosis and defective methylation. Hyperhomocysteinemia is associated with an increased risk of atherosclerotic and thromboembolic disorders, as well as hyperinsulinemia and may partially account for increased risk of cardiovascular disease associated with insulin resistance. Women with PCOS are more likely to develop components of the metabolic syndrome such as disturbances of carbohydrate metabolism, obesity, hypertension and dyslipidemia, which in turn are risk factors for cardiovascular disease. A number of studies confirmed the presence of increased serum homocysteine concentration in PCOS patients and the possible determinants of this observation are still debated. PCOS treatment options can influence homocysteine levels.