To define the effect of a history of cancer on in-hospital and long-term mortality after primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI). In this retrospective cohort study of 2346 patients with STEMI enrolled in the Mayo Clinic PCI registry from November 1, 2000, through October 31, 2010, we identified 261 patients (11.1%) with a history of cancer. The in-hospital and long-term outcomes (median follow-up, 6.2 years; interquartile range=4.3-8.5 years), including cardiac and noncardiac death and heart failure hospitalization, of these patients were compared with those of 1313 cancer-negative patients matched on age, sex, family history of coronary artery disease, and date of STEMI. Patients with cancer had higher in-hospital noncardiac (1.9% vs 0.4%; P=.03) but similar cardiac (5.8% vs 4.6%; P=.37) mortality as matched controls. The group at highest acute mortality risk were those diagnosed as having cancer within 6 months before STEMI (hazard ratio HR=7.0; 95% CI, 1.4-34.4; P=.02). At 5 years, patients with cancer had similar cardiac mortality (4.2% vs 5.8%; HR=1.27; 95% CI, 0.77-2.10; P=.35) despite more heart failure hospitalizations (15% vs 10%; HR=1.72; 95% CI, 1.18-2.50; P=.01) but faced higher noncardiac mortality (30.0% vs 11.0%; HR=3.01; 95% CI, 2.33-3.88; P<.001) than controls, attributable solely to cancer-related deaths. One in 10 patients in this contemporary registry of patients undergoing primary PCI for STEMI has a history of cancer. These patients have more than a 3 times higher acute in-hospital and long-term noncardiac mortality risk but no increased acute or long-term cardiac mortality risk with guideline-recommended cardiac care.