BACKGROUND: Information on practice patterns and outcomes in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary interventions (PCIs) in Canada vs United States is limited. METHODS: We evaluated differences in clinical and angiographic features, practice patterns, and outcomes between Canada and United States in 2,086 patients with ST-elevation myocardial infarction undergoing primary PCI in the APEX AMI trial. RESULTS: Of 2,086 patients, 335 (19%) were enrolled in Canada. Compared with US patients, Canadians were older with lower body mass index and creatinine clearance and less likely to have history of hypertension, smoking, or prior revascularization. Baseline infarct artery patency was higher, and the use of intra-aortic balloon pump and drug-eluting stents was lower in Canadian patients. Median door-to-PCI time was significantly shorter among Canadian patients (0.9 hours [interquartile range 0.6-1.3] vs 1.2 hours [interquartile range 0.8-1.7]). Clinical outcomes at 90 days were lower among Canadian patients, including shock (2.7% vs 4.2%), heart failure (3.6% vs 5.6%), bleeding (3.6% vs 9.6%), and atrial (3.6% vs 7.4%) and ventricular (3.0% vs 6.4%) arrhythmias. However, 90-day mortality (2.7% vs 4.8%, adjusted hazard ratio 0.62, 95% CI 0.47-1.28) and composite of death, shock, or heart failure (6.8% vs 11.5%, adjusted hazard ratio 0.77, 95% CI 0.47-1.27) were similar in the 2 cohorts. CONCLUSIONS: Compared with US patients, Canadian patients had shorter door-to-PCI time but similar 90-day outcomes. These data suggest an opportunity for US sites to examine and learn from the Canadian systems of processes of care and implement changes so as to improve the timeliness of primary PCI.