Chronic renal failure is an acknowledged late complication of BMT. It is related to the intensive chemotherapy, radiation and supporting medications. Polymorphism in the angiotensin converting enzyme (ACE) gene is associated with progression of nephropathy caused by diabetes and IgA nephropathy. We sought to determine whether ACE genotype and other clinical factors were associated with loss of renal function after BMT. We determined the genotype of 106 adult allogeneic BMT recipients, who received a similar preparative regimen, survived 1 year, and had assessment of renal function up to 3 years after BMT. We found that the distribution of genotypes was similar to the general population; 29%, 51%, and 20% for the DD, DI, and II genotypes, respectively. There was no statistical difference in patient survival between the three groups. Among all patients, the average creatinine clearance declined from 124 (95% CI 117, 131) to 89 (95% CI 78, 100) ml/min over the 36 months after BMT. Decline in renal function over time was less for patients with the DD compared to the II genotype (P = 0.040). Renal function in patients with the DD genotype was also better than those with the DI genotype, but this was of borderline statistical significance (P = 0.055). Renal shielding reduced decline in renal function compared to no shielding (P = 0.026). We conclude that the ACE genotype does not seem to influence survival, but the DD genotype may be protective against renal injury after BMT. Furthermore, we confirm that renal shielding during TBI reduces the renal injury after BMT.