PURPOSE: To assess the prevalence of metabolic syndrome and of its defining criteria in women with polycystic ovary syndrome from the Brazilian Southeast, who were stratified according to body mass index and compared to ovulatory controls. METHODS: This was a cross-sectional study conducted on 332 women of reproductive age, who were divided into two groups: Control, consisting of 186 women with regular menstrual cycles and ovulatory symptoms and without a diagnosis of polycystic ovary syndrome or other type of chronic anovulation, and the Polycystic ovary syndrome,Group, consisting of 146 women with a diagnosis of polycystic ovary syndrome (Rotterdam Consensus ASRM/ESHRE). Each group was stratified according to the body mass index, as follows: body mass index ( < 25 ≥25 and <30, and ≥ 30 kg/m²). The frequencies of metabolic syndrome and of its defining criteria and the clinical and hormonal characteristics (follicle stimulating hormone, total testosterone, dehydroepiandrostenedione sulfate) were analyzed. RESULTS: The frequency of metabolic syndrome was six times higher in the obese Polycystic ovary syndrome Group than among control women with the same body mass index (Control with 10.5 versus Polycystic ovary syndrome with 67.9%, p<0.01); twice higher in the Polycystic ovary syndrome Group with body mass index ≥ 25 and <30 kg/m² (Control with 13.2 versus Polycystic ovary syndrome with 22.7%, p<0.01), and three times higher in the Polycystic ovary syndrome Group with body mass index <25 kg/m² (Control with 7.9 versus Polycystic ovary syndrome with 2.5%, p<0.01), compared to control women paired for the same body mass index. Regardless of the body mass index, women with polycystic ovary syndrome had a higher frequency of all the criteria defining metabolic syndrome. CONCLUSION: Women with polycystic ovary syndrome have higher frequency of metabolic syndrome and of its defining criteria regardless of the body mass index. Hyperinsulinemia and hyperandrogenism are important characteristics of the origin of these alterations, especially in obese women with polycystic ovary syndrome.