Ovarian function was followed serially in a group of six postmenarcheal females after successful bone marrow transplantation (BMT). The patients were between 13 9/12 and 22 6/12 (median 16 5/12) years of age at the time of BMT and were followed a median of 20 months (range 17-45 months) posttransplantation. Two subjects received short-term high-dose cyclophosphamide combined with single-dose total lymphoid irradiation (Group I), whereas the remaining four were treated with short-term, high-dose chemotherapy plus single-dose total body irradiation (Group II). Group II subjects also received combination chemotherapy prior to BMT. One subject from Group I continues to have regular menses and normal gonadotropin levels, 36 months post-BMT. The remaining five patients have demonstrated persistently elevated plasma concentrations of LH and FSH over a 17- to 45-month period of time. None of the four patients in Group II has menstruated since undergoing BMT. We conclude that single-dose radiation combined with short-term, high-dose chemotherapy results in profound ovarian damage in the majority of young women undergoing BMT.