To compare the capacity of transvaginal Doppler ultrasound examination with that of gray scale sonography as an aid in distinguishing benign and malignant pelvic tumors of suspected adnexal origin. One hundred and fifty-one women scheduled for laparotomy or laparoscopic surgery because of a pelvic mass of suspected adnexal origin underwent ultrasound examination including color and spectral Doppler techniques within 8 days preceding the operation. Based on the gray scale ultrasound image, each tumor was classified as being either a unilocular cyst, a multilocular cyst, a unilocular cyst with solid parts, a multilocular cyst with solid parts or a solid tumor. Tumor vascularization was visualized with the color Doppler technique, each tumor being characterized by the color content of the scan, as rated subjectively on a visual analogue scale ('tumor color score'). Blood flow velocity waveforms were obtained by placing the Doppler gate over the colored area with the tumor. The blood flow velocity waveform with the highest time averaged maximum velocity was used to characterize the tumor . The results of gray scale imaging and Doppler ultrasound examination were compared with the histology of the specimen. Ultrasound morphology correctly identified all the malignant tumors, with a false-positive rate of 61%; none of the 49 unilocular or multilocular cysts without solid parts was malignant, whereas 24% (24/102) of the tumors with solid components were. Among multilocular cysts with solid parts, both tumor color scores and time average maximum blood flow velocities were significantly higher in malignant than in benign tumors, but among solid tumors there was complete overlap in Doppler results between the malignant and benign subgroups. Using Doppler examination to discriminate between benign and malignant multilocular cysts with solid parts and ultrasound morphology for differentiation of the remaining tumors, all the malignancies in the study were detected with a false-positive rate of 32 or 38% depending on which Doppler variable was used. The present technique of Doppler ultrasound examination is helpful only in the differential diagnosis of multilocular cysts with solid parts. Therefore, the degree to which Doppler examination can contribute to the differential diagnosis of pelvic tumors will depend on the proportion of multilocular cysts with solid parts in the population studied: the greater this proportion, the greater the potential of the Doppler examination to improve diagnostic accuracy.