Transvaginal pulsed color Doppler ultrasound was used to examine 72 patients with a pelvic mass preoperatively. Tumor morphology was assessed, prominent areas of vascularization within the tumor were observed and the pulsatility index and the resistance index of tumor and uterine arteries were measured. Flow velocity waveforms with low pulsatility are considered to reflect neovascularization. The ultrasound diagnoses were compared with histopathological or cytological diagnoses. There were 61 benign, eight malignant and three borderline cases. In 75% of the malignant and 23% of the benign tumors, an intratumoral flow with a low pulsatility was detectable. The mean pulsatility index of tumor blood vessels was 1.2 in benign, 0.7 in malignant and 0.6 in borderline neoplasms. The corresponding mean resistance index values were 0.6, 0.5 and 0.5. The differences were not significant and the overlap between the malignant and benign lesions was large. The pulsatility index and resistance index of uterine arteries were significantly decreased in malignant tumors. The results show that, using a cut-off resistance index value of 0.6, the sensitivity and specificity of color Doppler in the detection of malignant and potentially malignant tumors were 82% and 72%, respectively. However, a practical cut-off level for either pulsatility or resistance indices, that could assist in differentiating between malignant or benign lesions, does not seem to exist.