Objective To determine oxidative stress status and its association with clinical and metabolic parameters in Chinese women with different clinical phenotypes of polycystic ovary syndrome (PCOS). Design A cross-sectional study. Patients A total of 544 patients with PCOS and 468 control women were included. Measurements The total oxidant status (TOS) was determined using a microplate colorimetric method. Total antioxidant capacity (T-AOC), oxidative stress index (OSI, the ratios of TOS to T-AOC) and clinical, hormonal and metabolic parameters were also analysed. Results TOS and OSI were significantly higher in each of the four PCOS phenotypes based on the Rotterdam criteria than in the control women and higher in patients with hyperandrogenism (HA) than in those without HA (P < 0.05). TOS, T-AOC and OSI were higher in lean patients than in lean controls (P < 0.05). These values, except OSI, were also higher in overweight/obese patients than in lean patients, and lean or overweight/obese controls (P < 0.05). Multivariate regression analysis demonstrated that apolipoprotein (apo) A1, the Ferriman-Gallwey score, triglyceride (TG), oestradiol (E-2), high-density lipoprotein cholesterol (HDL-C) and 2-h glucose levels were the main predictors of TOS; the Ferriman-Gallwey score, E-2, apoA1, TG and HDL-C levels were the main predictors of OSI. Conclusions Patients with PCOS with HA have higher oxidative stress levels compared with those without HA. The increased oxidative stress in PCOS is related to HA status, increased plasma glucose, TG, HDL-C and E2 levels, decreased apoA1 concentrations and a relative shortage of antioxidant capacity.