The purpose of this study was to evaluate the effect of partial renal shielding used in conjunction with total body irradiation (TBI) on the incidence of bone marrow transplantation nephropathy (BMT Np) seen as a late sequelae after transplantation. Of 402 patients who have undergone bone marrow transplantation (BMT) at the Medical College of Wisconsin (MCW) 157 were greater than 18 years of age, received 14 Gy TBI and survived at least 100 days post-transplant. The incidence of BMT nephropathy was evaluated in these patients by dose to the kidneys. In the 72 patients who received 14 Gy TBI with no renal shielding, the actuarial risk of developing BMT Np at 2 1/2 years (30 months) post-BMT was 29 +/- 7%. Sixty-eight patients received 14 Gy TBI with partial renal shielding of 15% (renal dose = 11.9 Gy), the actuarial risk of developing BMT Np was 14 +/- 5% at 2 1/2 years. Seventeen patients received 14 Gy TBI with renal shielding of 30% (renal dose = 9.8 Gy); none of this group have developed BMT Np despite a median follow-up of over 2 1/2 years (985 days). The trend of decreasing BMT Np with increasing shielding is statistically significant (P = 0.012). Prognostic factors such as age, type of transplant and good-risk vs poor-risk disease status were evaluated and were similar in each cohort of patients described above. We conclude that given the statistically significant benefit seen here in the reduced incidence of BMT Np by the use of selective renal shielding, this should be seriously considered for all patients who receive TBI, but especially for patients whose renal doses exceed 10 Gy.