Two thousand and nine hundred real-time ultrasonographic examinations were performed in the outpatient Department of Obstetrics and Gynecology at Hirata Municipal Hospital, Japan from April '84 to September '86,and polycystic ovaries were detected in 28 patients. Characteristic internal structures of polycystic ovaries were general cystic and peripheral cystic ovaries. In 26 out of the 28 for whom the bilateral ovaries were assessed ultrasonographically, bilateral peripheral cystic ovaries were identified in 12 (46.2%), peripheral and general cystic ovaries in 7 (26.9%), peripheral cystic ovarty and homogenous ovary in 4 (15.4%), and peripheral cystic ovary and dominant single cystic ovary in 3 (11.5%), respectively. The clinical symptoms in each patient varied and sterility was evident in 6 of the 28. Ultrasonography proved to be a non-invasive diagnostic tool for the primary screening of the polycystic ovary and is most economic of time.