Status of the endometrium was assessed in 357 patients with hormone-producing tumors of the ovaries of major histological types such as theca cell (161 cases), granulosa cell (123) and mixed theca-granulosa cell tumors (22) as well as androblastoma (23) and Brenner's tumor (28 patients). Hyperplastic lesions of the endometrium, cancer included, were established in 250 (74.8%) patients with feminizing hormone-producing tumors whereas androblastoma patients showed either atrophic or normal endometrium (78.3% cases) and failed to reveal atypical hyperplasia or cancer of that site.