The objective of this study was to determine whether obese patients with polycystic ovary syndrome (PCOS) show different ovarian and uterine blood flow patterns in comparison with lean patients. Sixteen obese (body mass index: BMI = 31.4 +/- 3.6 kg/m2) and 22 lean (BMI = 21.1 +/- 1.3 kg/m2) PCOS patients underwent, in the early follicular phase if oligomenorrheic or randomly if amenorrheic, ultrasonographic evaluation of ovarian volume, echodensity and follicle number; transvaginal color Doppler evaluation of uterine and intraovarian blood flow; and radioimmunological assay of luteinizing hormone, follicle stimulating hormone, growth hormone, estradiol, progesterone, testosterone, androstenedione, insulin, insulin-like growth factor I, and other hormonal parameters. Hematocrit, plasma glucose, total cholesterol, high density lipoprotein and triglycerides were also evaluated. Insulin levels were significantly higher in the obese group, whereas levels of growth hormone were significantly lower. Moreover, a more adverse lipid profile was observed in overweight patients. This was associated with higher hematocrit values. At Doppler analysis, a significantly higher mean uterine artery pulsatility index (PI) was observed in the obese group. Furthermore, the PI was inversely correlated with high density lipoprotein values (r = -0.4820; p < 0.05). In both groups, androstenedione was correlated with the uterine PI. The above findings may, in part, explain the increased risk in women with PCOS of developing cardiovascular diseases, and emphasize that obesity may further increase the risk.