Background: Numerous previous studies have shown that renal insufficiency (RI) in patients with acute coronary syndrome is associated with poor cardiovascular outcomes. These studies do not well address the impact of RI on the long-term outcome of patients with acute ST-elevation myocardial infarction (STEMI) in China. The aim of this study was to investigate the association of admission RI and inhospital and long-term mortality of patients with acute STEMI. Methods: This was a multicenter, observational, prospective-cohort study. 718 consecutive patients were admitted to 19 hospitals in Beijing within 24 hours of onset of STEMI, between January 1,2006 and December 31,2006. Estimation of glomerular filtration rate (eGFR) was calculated using the modified abbreviated modification of diet in renal disease equation-based on the Chinese chronic kidney disease patients. The patients were categorized according to eGFR, as normal renal dysfunction (eGFR >= 90 ml.min(-1).1.73 m(-2)), mild RI (60 ml.min(-1).1.73 m(-2) <= eGFR < 90 ml.min(-1) 1.73 m(-2)) and moderate or severe RI (eGFR < 60 ml.min(-1).1.73 m(-2)). The association between RI and inhospital and 6-year mortality of was evaluated. Results: Seven hundred and eighteen patients with STEMI were evaluated. There were 551 men and 167 women with a mean age of 61.0 +/- 13.0 years. Two hundred and eighty patients (39.0%) had RI, in which 61 patients (8.5%) reached the level of moderate or severe RI. Patients with RI were more often female, elderly, hypertensive, and more patients had heart failure and stroke with higher killip class. Patients with RI were less likely to present with chest pain. The inhospital mortality (1.4% vs. 5.9% vs. 22.9%, P < 0.001), 6-year all-cause mortality (9.5% vs. 19.8 vs. 45.2%, P < 0.001) and 6-year cardiac mortality (2.9% vs. 12.2% vs. 23.8%, P < 0.001) were markedly increased in patients with RI. After adjusting for other confounding factors, classification of admission renal function was an independent predictor of inhospital mortality (Odd ratio, 1.966; 95% confidence interval [CI], 1.002-3.070, P = 0.019), 6-year all-cause mortality (relative risk [RR]= 1.501, 95% CI: 1.018-4.373, P = 0.039) and 6-year cardiac mortality (RR = 1.663, 95% CI: 1.122-4.617, P = 0.042). Conclusions: RI is very common in STEMI patients. RI evaluated by eGFR is an important independent predictor of short-term and long-term outcome in patients with acute STEMI.