In this prospective cohort study we analyzed the impact of admission renal function on the hospital course of 2,503 patients with unstable angina pectoris (UAP) and acute myocardial infarction (AMI). The patients were stratified into quartile groups (Q1 to Q4) defined by baseline corrected creatinine clearance (cCrCl) values of 51.4, 63.8, and 76.8 mg/min/72 kg. The proportions of patients with a discharge diagnosis of AMI increased with declining cCrCl, from 35.5% in Q4 to 46.0% in Q1 (p <0.0001). The frequency of left ventricular (LV) failure (Q4 4.5%, Q1 31.0%, p <0.0001) and cardiac death (Q4 0.5%, Q1 9.5%, p <0.0001) also increased linearly with decreasing cCrCl, with no evidence that the prognostic impact of renal dysfunction was different in AMI or UAP (p for interaction 0.15). Logistic regression analysis confirmed the independent effects of cCrCl on outcome, with odds of LV failure and cardiac death for patients in Q4 being 0.34 (95% confidence intervals 0.16 to 0.72) and 0.14 (95% confidence intervals 0.03 to 0.74), respectively, relative to patients in Q1. No threshold was detected for the adverse effects of renal dysfunction on outcomes; the log odds of LV failure and cardiac death against quartiles of cCrCl both showed significant linear trends (p <0.0001) with each change in quartile, resulting in risk reductions of 55% (odds [SE] 0.45 [0.03]) and 65% (odds [SE]: 0.35 [0.05]), respectively. In conclusion, renal function showed a graded association with LV failure and hospital death that was independent of diagnosis (UAP or AMI) and other baseline variables. There was no detectable threshold of renal dysfunction for these adverse prognostic effects.