To compare spatiotemporal image correlation-high definition flow (STIC-HDF) indices from spherical samples of ovary between women with polycystic ovary syndrome (PCOS) and normal women. This was a prospective case-control study of premenopausal women with a diagnosis of PCOS according to the Rotterdam criteria and of healthy, regularly menstruating, premenopausal women (controls) matched for age (< 35 years) and body mass index. Women were assessed in the follicular phase of the menstrual cycle by 4D STIC-HDF transvaginal ultrasound. Based on 1-cm(3) spherical sampling, we calculated for each woman the vascularization index (VI) for the most vascularized part of the ovarian stroma in all three-dimensional volumes of the 4D STIC-HDF sequence. The maximum (VI(sys)) and minimum (VI(diast)) values were assumed to represent systole and diastole, respectively, and the mean VI for all frames from one cardiac cycle was calculated. Based on these three VI values, we calculated the following indices: volumetric systolic/diastolic ratio (vS/D), volumetric resistance index (vRI) and volumetric pulsatility index (vPI), and compared them between study and control groups. The study included 32 PCOS women (mean age, 29.6 years) and 32 controls (mean age, 30.4 years). Mean VI(sys) (26.246% vs 8.136%, P < 0.0001) and mean VI(diast) (22.242% vs 5.997%, P < 0.0001) were significantly higher in PCOS women compared with controls. Median vS/D (1.15 vs 1.33, P < 0.001), mean vRI (0.17 vs 0.30, P < 0.001) and median vPI (0.14 vs 0.28, P < 0.001) were significantly lower in PCOS women compared with controls. 4D STIC-HDF indices from 1-cm(3) spherical samples of the ovaries were different between PCOS women and controls, suggesting lower impedance to flow in ovarian stromal vessels in PCOS women.