Ultrasonography is most commonly utilized diagnostic tool in obstetric and gynecology for the evaluation of patient with a pelvic mass or pregnancy. For it is charcterized by no radiation hazard. noninvasive examination and high diagnostic accuracy. Also it affords an accurate assessment of the presence, size, location and internal consistency of a pelvic mass. The recent availability and improved resolution of realtime scanning have afforded a more flexible and complete approach to evaluation of normal and abnormal structures in the pelvis. We analyzed ultrasonographic findings in 154 pathologically proven cases of pelvic mass examined at Korea General Hospital from January 1983 to April 1984. The results were as follows: 1. The age distribution was from 12 years to 66 years and the majority of patients were between the ages of 21 and 50 years (91.4%) 2. The incidence of pelvic mass was 27.9% in uterine leiomyoma, 22.7% in ovarian cyst, 13.0% in adenomyosis and 8.4% in serous cystadenoma. 3. Mild to moderately echogenic nodular uterine enlargement with some cystic change (81.4%) of leiomyoma and multiple small vesicular pattern of intrauterine contents with uterine enlargement of H-mole were the most common ultrasonographic findings. The location and type of leiomyoma were most common in the fundus and body (95.3%), and intramural myoma (53.5%) The most frequent finding of ovarian teratoma was cystic mass with echogenic focus (41.7%) but the echogenic appearance of the lesions was extremely variable. The most frequent finding of ovarian teratoma was cystic mass with echogenic focus (41.7%) but the echogenic appearance of the lesions was extremely variable. The most frequent finding of ovarian teratoma was cystic mass with echogenic focus (41.7%) but the echogenic appearance of the lesions was extremely variable. The ultrasonographic findings of ectopic pregnancy were cystic or complex adnexal mass (80.0%) with or without fluid in cul-de-sac and deviation of uterus by adnexal mass. 4. Accuracy of ultrasonography in determining the overall correct diagnosis of the pelvic masses compared with proven diagnosis was approximately 61.7% The diagnostic accuracy was 90.7% in uterine leiomyoma, 100% in H-mole and 80.0% in ectopic pregnancy.