Stein-Leventhal syndrome is a clinicopathological entity characterized by chronic anovulation and sclerotic ovaries. Clinically, the affected patients typically present their third decade with a history of premenarchal obesity and postmenarchal onset of oligomenorrhea or amenorrhea, infertility, and clinical evidence of increased androgen production. In some patients, there are estrogenic phenomena such as menometrorrhagia with or without endometrial hyperplasia or carcinoma. Several studies have indicated that there may be an increased incidence of ovarian neoplasia in polycystic ovaries. Recently, we experienced two cases of polycystic ovaries assotiated with endometrial carcinoma in premenopausal women, who had clinical characteristics of Stein-Leventhal syndrome; one of the cases had additional serous cystandenofibroma.