Background: Women with polycystic ovary syndrome (PCOS) are at high risk for the development of diabetes mellitus, hypertension and coronary heart disease. Due to the inverse correlation between serum uric acid and insulin sensitivity, the measurement of uric acid may provide a marker of insulin resistance. Objective: To establish the relationship between uric acid and markers of insulin resistance in obese and overweight women with PCOS. Methods: Serum uric acid levels were measured in 38 PCOS obese and overweight patients and 30 controls matched for age and body mass index (BMI). Anthropometric variables, plasma glucose and insulin levels were measured. Insulin resistance was evaluated by homeostasis model assessment (HOMA-IR). Results: No statistically significant differences in uric acid levels between PCOS and non-PCOS women were found. Serum uric acid levels were positively correlated with BMI, waist circumference, insulin and HOMA. Following the use of stepwise linear regression analysis, BMI was the only parameter retained by the regression model, responsible for 42.1% of the variability of serum uric acid levels. Conclusions: In PCOS women obesity seems to be the main determinant of plasma uric acid levels. Insulin and HOMA are also involved to a lesser extent, but their role remains to be clarified by further studies.