Guidelines support percutaneous coronary intervention (PCI) of the noninfarct-related artery during primary PCI for ST-segment elevation myocardial infarction (STEMI) in patients with hemodynamic compromise; however, in patients without hemodynamic compromise, PCI of the noninfarct-related artery is given a class III recommendation. We analyzed the National Cardiovascular Data Registry (n = 708,481 admissions, 638 sites) to determine the prevalence, predictors, and in-hospital outcomes of primary multivessel PCI from 2004 to 2007. Patients with STEMI and multivessel coronary artery disease who were undergoing primary PCI were identified (n = 31,681). After excluding the patients treated with staged PCI (n = 2,745), 10.8% (n = 3,134) of the remaining population (n = 28,936) were treated with multivessel PCI. Patients undergoing multivessel PCI were at higher risk and were more likely to be in cardiogenic shock. The overall in-hospital mortality rates were greater in patients undergoing multivessel PCI (7.9% vs 5.1%, p <0.01). Among patients with STEMI and cardiogenic shock (n = 3,087), those receiving multivessel PCI had greater in-hospital mortality (36.5% vs 27.8%; adjusted odds ratio 1.54, 95% confidence interval 1.22 to 1.95). In conclusion, these data suggest that performing multivessel PCI during primary PCI for STEMI does not improve short-term survival even for patients with cardiogenic shock. These findings suggest the need for definitive studies to evaluate the utility of noninfarct-related artery PCI among patients with STEMI.