OBJECTIVE: The aim of this study was to assess the effects of the Dietary Approaches to Stop Hypertension (DASH) diet on lipid profiles and biomarkers of oxidative stress in overweight and obese women with polycystic ovary syndrome (PCOS). METHODS: This randomized controlled clinical trial was conducted with 48 women diagnosed with PCOS. The women were randomly assigned to consume either the control (n = 24) or DASH diet (n = 24) for 8 wk. Both diets were designed to be calorie-restricted. Both diets consisted of 52% carbohydrates, 18% proteins, and 30% total fats. The DASH diet was designed to be rich in fruits, vegetables, whole grains, and low-fat dairy products and to be low in saturated fats, cholesterol, and refined grains. Fasting blood samples were taken at baseline and after 8-wk intervention to measure lipid profiles and biomarkers of oxidative stress including plasma total antioxidant capacity (TAC) and total glutathione (GSH). RESULTS: Adherence to the DASH diet, compared with the control diet, resulted in a significant decrease in weight (-4.4 versus -1.5 kg; P < 0.001) and body mass index (-1.7 versus -0.6 kg/m(2); P < 0.001), decreased serum triglycerides (-10.0 versus +19.2 mg/dL; P interaction = 0.005) and very-low-density lipoprotein cholesterol levels (-2.0 versus +3.9 mg/dL; P interaction = 0.005). Increased concentrations of TAC (+98.6 versus -174.8 mmol/L; P interaction <0.001) and GSH (+66.4 versus -155.6 μmol/L; P interaction = 0.005) also were found in the DASH group compared with the control group. CONCLUSION: Consumption of DASH diet for 8 wk led to a significant reduction in serum insulin, triglycerides and very-low-density lipoprotein cholesterol and a significant increase in TAC and GSH levels.