We reviewed gonadal function in 270 patients who underwent bone marrow transplantation (BMT) between 1974 and 1988. Age at transplant ranged from 6 to 54 years (mean 25.6 years). Diagnoses included acute myelogenous leukemia, chronic myelogenous leukemia, aplastic anemia, acute lymphoblastic leukemia, non-Hodgkin lymphoma, Hodgkin's disease and other diagnoses. Effects of patient characteristics on risk of gonadal dysfunction were analyzed by comparing the cumulative probability of developing gonadal dysfunction over time from BMT. Ninety-two percent of the males and 99% of the females developed evidence of gonadal dysfunction. Females were not only more likely to develop elevated gonadotrophin levels than males, but did so earlier after BMT. Odds ratios were calculated to determine potentially important prognostic factors for the development of an elevated gonadotrophin level. Older age at BMT was correlated with an increased risk in the development of elevated gonadotrophin levels. Individuals who received radiation were more likely to develop an elevated FSH level over time than those who had received no preparative radiation treatment. Males were more likely to experience gonadal recovery than females. In those cases that did recover, males tended to recover more quickly after BMT than females.