In a retrospective study, we compared transvaginal sonograms with transabdominal sonograms in 67 women referred for evaluation of palpable pelvic masses. The diagnoses included ovarian cyst (27), endometrioma (12), complex cyst (four), dermoid (three), infection (three), ovarian malignancy (two), and uterine fibroid (three). The final diagnosis was made surgically in 41 patients (61%) and by a combination of sonographic and clinical correlation in the remaining patients. More information about the internal architecture or anatomy of the mass was provided by the transvaginal images than by the transabdominal scans in 51 (76%) of the patients. Transabdominal sonography did not provide more diagnostic information in any of the patients examined. Transvaginal sonography was helpful in obese patients, in those with a large amount of bowel gas, and in those unable to achieve adequate bladder filling. Six simple cysts and four complex pelvic masses were identified solely on transvaginal sonograms. The results suggest that transvaginal sonography has considerable advantages over conventional transabdominal sonography in the evaluation of pelvic masses in women.