The purpose of this study was to assess the blood flow characteristics of adnexal masses before surgical excision and to determine whether color flow Doppler sonography is useful for distinguishing benign from malignant masses. Thirty-one adnexal masses were evaluated with color flow Doppler transvaginal sonography. The pulsatility index and resistive index were calculated from the waveforms generated from blood flow within the ovary. Twenty-five lesions were benign and six were malignant on pathologic examination. Benign lesions included six endometriomas, six mesothelial cysts, three serous and one mucinous cystadenoma, three mature cystic teratomas, two hemorrhagic corpus luteum cysts, one cystadenofibroma, one sclerosing stromal cell tumor, one paratubal cyst, and one ovary that had undergone torsion with infarction. The malignant lesions consisted of three papillary serous cystadenocarcinomas, one granulosatheca cell tumor, one immature teratoma, and one metastasis of colon cancer to the ovaries. Benign tumors and cysts had a significantly higher pulsatility index (mean, 1.93 +/- 1.02; range, 0.23-3.99) and resistive index (mean, 0.77 +/- 0.22; range, 0.2-1.0) than did malignant tumors (pulsatility index: mean, 0.77 +/- 0.33; range, 0.31-1.09; resistive index: mean, 0.5 +/- 0.17; range, 0.27-0.67). However, some overlap in individual values for benign and malignant lesions was found. Our preliminary data suggest that high pulsatility and resistive indexes indicate benign adnexal processes; however, considerable overlap in pulsatility and resistive indexes between benign and malignant lesions was noted, and further work is needed before the validity of these factors is proved.