OBJECTIVE: Ovarian failure is often common complication by the conditioning protocol used for bone marrow transplantation (BMT). To determine the frequency of recovery of ovarian function after allo-BMT and the major factor that predict recovery, we monitored ovarian function in 24 premenopausal women METHOD: Twenty-four women met the inclusion criteria, which were (1) moderate to severe aplastic anemia before BMT, (2) disease-free at least 18 month after transplantation, (3) age younger than 40 years and more than 3 years after menarche at transplantation and (4) regular menstrual periods before transplantation. Recovery of ovarian function was determined by regular menses without menopausal symptom and sign. we divided conditioning regimen to two groups, Group I : cytoxan alone(n=17), Group II : cytoxan plus total body irradiation (TBI)(n=7). RESULTS: All women became amenorrhea after BMT and the clinical characteristics were not significant between two groups. 17 patients who received only cytoxan all recovered ovarian function between 1 to 14 months(median : 7.28) after BMT. The median age at BMT of women with regained ovarian function was 26 years (range, 21 to 33) versus 30 (range, 21 to 37) for those who did not. The age at transplantation was not significant between two groups in our study and the most predictive independent factor in ovarian recovery is the presence of total body irradiation. None of women who received TBI regained ovarian function during 19-49 month follow up. CONCLUSION: Gonadal insufficiency due to pre-BMT conditioning is more severe in radiation based regimen than cytoxan alone. therefore, we recommend early hormone replacement therapy in radiation treated women to prevent the complication of premature menopause.