Renal insufficiency has been identified as a risk factor for graft loss and death after renal transplantation but has not been consistently linked to early, nonfatal, hospitalized heart disease (HHD). With the United States Renal Data System database, 29,597 patients who received a kidney transplant between January 1, 1996, and July 31, 2000, with Medicare as the primary payer, and were monitored until December 31, 2000, were studied. Cox proportional-hazards regression models were used to calculate the association of recipient estimated GFR (eGFR) at 1 yr after renal transplantation, as determined with the Modification of Diet in Renal Disease formula, with hospitalization for treatment of acute coronary syndromes (ACS) (International Classification of Diseases, version 9, code 410.x or 411.x) or congestive heart failure (CHF) (code 428.x) 1 to 3 yr after renal transplantation. Rates of ACS and CHF were 2.2 and 4.9%, respectively, for patients with eGFR of <44.8 ml/min per 1.73 m(2), compared with 1.2 and 1.4% for patients with eGFR of >69.7 ml/min per 1.73 m(2). Reduced eGFR (<44.8 ml/min per 1.73 m(2), compared with >69.7 ml/min per 1.73 m(2)) at the end of the first 1 yr after transplantation was independently associated with increased risks of both ACS (adjusted hazard ratio, 2.16; 95% confidence interval, 1.39 to 3.35) and CHF (adjusted hazard ratio, 2.95; 95% confidence interval, 2.24 to 3.90). It was concluded that early renal insufficiency (approximately stage 3 chronic kidney disease) was associated with higher rates of HHD 1 to 3 yr after kidney transplantation. Preservation of renal function after renal transplantation may reduce the rates of HHD, and renal transplant recipients with reduced eGFR should be considered at high risk of developing cardiovascular disease.