While the impact of prior coronary artery bypass graft surgery (CABG) on in-hospital outcomes in patients with ST-elevation myocardial infarction (STEMI) has been described, data are limited on patients with prior percutaneous coronary intervention (PCI) undergoing primary PCI in the setting of an STEMI. The aim of the present study was to assess the effect of previous revascularization on in-hospital outcomes in STEMI patients undergoing primary PCI. Between January 2004 and December 2007, a total of 1649 patients underwent primary PCI for STEMI at four New York State hospitals. Baseline clinical and angiographic characteristics and in-hospital outcomes were prospectively collected as part of the New York State PCI Reporting System (PCIRS). Patients with prior surgical or percutaneous coronary revascularization were compared to those without prior coronary revascularization. Of the 1649 patients presenting with STEMI, a total of 93 (5.6%) had prior CABG, 258 (15.7%) had prior PCI, and 1298 (78.7%) had no history of prior coronary revascularization. Patients with prior CABG were significantly older and had higher rates of peripheral vascular disease, diabetes mellitus, congestive heart failure, and prior stroke. Additionally, compared with those patients with a history of prior PCI as well as those without prior coronary revascularization, patients with previous CABG had more left main interventions (24% vs 2% and 2%; P<.001), but were less often treated with drug-eluting stents (47% vs 61% and 72%; P<.001). Despite a low incidence of adverse in-hospital events, prior CABG was associated with higher all-cause in-hospital mortality (6.5% vs 2.2%; P=.012), and as a result, higher overall MACE (6.5% vs 2.7%; P=.039). By multivariate analysis, prior CABG (odds ratio, 3.40; 95% confidence interval, 1.15-10.00) was independently associated with in-hospital mortality. In contrast, patients with prior PCI had similar rates of MACE (4.3% vs 2.7%; P=.18) and in-hospital mortality (3.1% vs 2.2%; P=.4) when compared to the de novo population. Patients with a prior history of CABG, but not prior PCI, undergoing primary PCI in the setting of STEMI have significantly worse in-hospital outcomes when compared with patients who had no prior history of coronary artery revascularization. Thus, only prior surgical - and not percutaneous - revascularization should be considered a significant risk factor in the setting of primary PCI.