OBJECTIVES: We investigated the relative benefit of reperfusion strategies in renal dysfunction and ST-segment elevation/left bundle branch block (STE/LBBB). BACKGROUND: Few data are available informing the treatment of STE myocardial infarction in the presence of renal dysfunction. METHODS: Patients (N = 12,532) from the GRACE (Global Registry of Acute Coronary Events) presenting with STE/LBBB were stratified by renal function and receipt of fibrinolysis, primary percutaneous coronary intervention (PCI), or neither. RESULTS: As renal function declined, hospital mortality increased and reperfusion decreased (both p < 0.001). Compared with no reperfusion, primary PCI was associated with lower hospital mortality in patients with normal renal function (1.9% vs. 3.7%, p = 0.001, adjusted) but no reduction in those with renal dysfunction (14% vs. 15% for glomerular filtration rate [GFR] 30 to 59 ml/min/1.73 m(2); 29% vs. 32% for GFR <30 ml/min/1.73 m(2)). Fibrinolysis was not associated with lower hospital mortality for normal (3.1% vs. 3.7%, p = NS) or low renal function (32% vs. 32%, p = NS) and with higher mortality with moderate renal dysfunction (adjusted odds ratio: 1.35, 95% confidence interval: 1.01 to 1.80). Primary PCI was associated with increased hospital bleeding and fibrinolysis with increased stroke in all patients. Among hospital survivors, primary PCI, but not fibrinolysis, was associated with lower mortality for moderate dysfunction. Both reperfusion strategies were associated with higher mortality for severe dysfunction. CONCLUSIONS: In STE/LBBB and renal dysfunction, mortality rates are high and reperfusion rates are lower. In moderate renal dysfunction, primary PCI is associated with mortality reduction at 6 months. Outcomes remain poor with severe renal dysfunction, despite receipt of reperfusion therapy.