Ten patients with ovarian bleeding, who were surgically treated, had been preoperatively evaluated using transvaginal color Doppler ultrasound. The blood-flow velocity waveforms of the bleeding also were analyzed. The bleeding artery of the ovary was clearly detected in 9 of 10 (90%) patients by transvaginal color Doppler ultrasound and was later confirmed by either a laparotomy or laparoscopic surgery. Either a corpus luteum cyst or a ruptured corpus luteum was associated with the bleeding in the 9 of the 10 patients. The resistance-index value in each bleeding artery examined in the 9 cases was relatively low, ranging from 0.46 to 0.59 (mean: 0.51). Based on our findings, transvaginal color Doppler ultrasound is useful for preoperatively detecting bleeding arteries in clinically severe cases of ovarian bleeding.