Background: Previous studies have demonstrated that impaired renal function is associated with unfavourable outcomes in patients with acute coronary syndromes and following percutaneous coronary intervention. Methods: We hypothesized that serum creatinine (Cr) on admission is a useful predictor of mortality in fibrinolytic-eligible patients with ST-elevation myocardial infarction (MI). Data were collected from 352 patients with ST-elevation MI, 89% of patients underwent early invasive management. Results: 30-day and 6-month mortality were increased among patients with mild to moderate (Cr > 1.2-2.8 mg/dl) renal dysfunction compared to patients with normal (Cr less than or equal to 1.2 mg/dl) renal function (3.4% vs. 16.1%, p < 0.001 and 4.5% vs. 19.5%, p < 0.001). After adjustment for previously identified correlates of mortality in a multiple logistic regression model, higher Cr on admission remained independently associated with increased mortality (30-day, OR 4.78, 95% CI 1.55-14.73, p = 0.006; 6-month, 3.82 (1.45-10.11), p = 0.007). The incidence of mortality was reduced among those patients with renal dysfunction that also underwent acute percutaneous coronary intervention [30-day, OR 0.13, 95% CI 0.02-1.06, p < 0.03; 6-month, 0.23 (0.05-1.07), p < 0.05]. Conclusion: Cr on admission is a strong and independent predictor of mortality in patients with ST-elevation MI. This association does not appear to be mediated by reduced fibrinolytic efficacy, or by higher reinfarction rates among patients with renal dysfunction. Cr on admission is a rapid and widely available marker to identify high-risk patients with ST-elevation MI that have additional improvements in survival when treated with percutaneous coronary intervention.