OBJECTIVE: To analyze retrospectively the frequency, long-term prognosis and pregnancy rate in infertile women diagnosed with endometrial hyperplasia or carcinoma by endometrial biopsy. STUDY DESIGN: From 1989 to 2000, endometrial biopsies were performed on 2,573 patients to investigate the cause of infertility. The main outcome measures were frequency, long-term prognosis and pregnancy rate for patients with each type of endometrial abnormality. RESULTS: Twenty-four patients (0.93%) were diagnosed with an endometrial abnormality. Of them, 10 were diagnosed with simple hyperplasia, 7 with complex hyperplasia, 3 with complex hyperplasia with atypia and 4 with endometrial carcinoma. All 4 patients (0.16%) with endometrial carcinoma were infertile as a result of complications arising from polycystic ovary syndrome. Two of them underwent hysterectomies. High-dose medroxyprogesterone acetate therapy combined with assisted reproductive technology resulted in pregnancy in 1 of the 2 patients with endometrial carcinoma. CONCLUSION: Of infertile women, 0.93% have endometrial abnormalities, and those with polycystic ovary syndrome have a high risk of endometrial carcinoma. Assisted reproductive technology combined with high-dose medroxyprogesterone acetate may be effective means of overcoming infertility, allowing women with endometrial carcinoma to readily achieve pregnancy.