OBJECTIVE The impact of posttransplantation anemia on patient survival, renal allograft survival, and rate of acute rejection is not known. METHODS A total of 1023 patients who underwent kidney transplantation at one center from January 1992 through June 2003 were retrospectively analyzed. Posttransplantation anemia was defined as mean hemoglobin <11 g/dl after 3 mo after transplantation. Data on demographics, pretransplantation dialysis, previous transplant history, pretransplantation hemoglobin, degree of HLA mismatch, and donor characteristics were collected. Some of the posttransplantation data that were collected in addition to the hemoglobin included delayed graft function; diabetes; hypertension; induction and maintenance of immunosuppressive regimen; posttransplantation infections; and use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker, statins, aspirin, and beta blockers. Cox regression models were used to assess the effects of posttransplantation anemia on each outcome: Mortality, graft survival, and rate of acute rejection. Median follow-up time was 4 yr. RESULTS During the entire follow-up period, there were 89 (9%) deaths, 143 (14%) acute rejection episodes, and 235 (23%) kidney losses. In multivariate Cox regression models, being anemic after transplantation, after the first 90 d, was associated with increased overall mortality and increased renal allograft loss. Posttransplantation anemia was also associated with increased acute rejection rates. CONCLUSIONS This study shows that posttransplantation anemia is associated with worse patient and graft survival and higher rates of acute rejection when compared with nonanemic renal transplant recipients.