Objective: To investigate the effect of continuous-combined hormone replacement therapy (HRT) on ovarian circulation, we used three-dimensional power Doppler ultrasound to assess ovarian stromal blood flow in postmenopausal women. Design: Forty healthy, postmenopausal women were enrolled in this prospective, controlled study. They were divided into two groups: the control group (20 patients with no HRT treatment) and the HRT group [initially 20 patients, but later 15 patients who completed the study, using continuous-combined conjugated equine estrogen (0.625 mg/day) plus medroxyprogesterone (5 mg/day)]. All patients underwent transvaginal three-dimensional power Doppler ultrasonography at the time of recruitment and 3 months later. The ovarian stromal flow indices, including vascularization-flow index (VFI), flow index (FI), and vascularization index (VI), were measured. Blood withdrawals for serum follicle-stimulating hormone and estrogen level testing were obtained before and after 3 months of treatment. Results: All the variables in the hormone profile showed significant difference (P < 0.05) after 3 months of treatment in the HRT group. Of interest, the three-dimensional power Doppler indices of ovarian stromal flow, VFI (0.13 +/- 0.11 --> 0.59 +/- 0.49), FI (30.47 +/- 12.06 --> 38.41 +/- 10.21), and VI (0.31 +/- 0.27 --> 1.12 +/- 0.95) all showed significant increase (P < 0.05) after 3 months of HRT treatment. Conclusions: There was a significant increase in ovarian stromal flow indices after 3 months of treatment in the HRT group, but not in the controls. Monitoring the ovarian flow changes by three-dimensional power Doppler may be of clinical importance when HRT is given.