BACKGROUND: The aim of this study was to evaluate metabolic syndrome frequency, cardiovascular risk profile and premature carotid artery atherosclerosis in patients with polycystic ovary syndrome (PCOS) especially during early adulthood. METHODS: A case-control study was conducted on 43 young women (18-22 years of age) with PCOS and 43 age-matched volunteer controls. Anthropometrical measurements, hormone levels, lipid and glucose profile were obtained from all subjects. Two different criteria were used to assess metabolic syndrome (MS) frequency. Common carotid artery intima-media thickness (IMT) was measured and stepwise multiple linear regression analysis was used to identify the independent cardiovascular risk factors that predict IMT. RESULTS: MS was diagnosed in 11.6% (n=5) of women with PCOS compared to no cases in the control group (P=0.02). The mean IMT was significantly higher in PCOS subjects (0.746 +/- 0.106 mm) compared to controls (0.608 +/- 0.105 mm, P < 0.001). Among many cardiovascular risk factors evaluated, the diagnosis of PCOS, increased body mass index and decreased sex hormone-binding globulin were significant independent predictors of increased IMT. CONCLUSIONS: These findings indicate that adolescence may be a more appropriate time to intervene for PCOS patients, as many cardiovascular risks are already present during early adulthood. As far as IMT is concerned, mechanisms other than hyperandrogenaemia and obesity might be operating as causative factors.