BACKGROUND: This study was designed to establish appropriate body mass index (BMI) level for PCOS women and to compare metabolic abnormalities between PCOS women and control women in Southern China. METHODSThis clinical cross-sectional study included 999 PCOS patients (857 adults and 142 adolescents) and 922 age-matched controls (742 adults and 180 adolescents).RESULTS:The proportion of PCOS patients with a BMI above 23 kg/m² was 34.63. Serum insulin, triglycerides, waist and waist/hip (W/H) measurements were all correlated positively with BMI in PCOS women. Prevalence of metabolic syndrome in Chinese PCOS patients was 18.9. Receiver-operating characteristic analysis suggested that at the point of BMI ≥23 kg/m², the diagnostic power to detect metabolic disorders was at its best.CONCLUSIONSPCOS patients with a BMI of 23 kg/m² or beyond may have a higher risk of metabolic disorders. Using an appropriate BMI level may help to improve attention to metabolic disorders among PCOS patients in Southern China. © 2010 The Author.