Background Reperfusion with primary percutaneous intervention (PCI) in ST-segment elevation myocardial infarction leads to improved clinical outcomes. The contribution angiographic vs electrocardiographic reperfusion parameters confer on prognosis is unclear. Methods A prespecified subset of the APEX-AMI trial patients was analyzed by independent angiographic and electrocardiographic core laboratories (n = 1,018). Angiographic reperfusion after PCI and electrocardiogram 30 minutes post-PCI were assessed. Results Of the 941 patients in the angiographic substudy, 796 (85%) attained post-PCI Thrombolysis In Myocardial Infarction (TIMI) flow 3 and 852 (91%) had TIMI Myocardial Perfusion Grade (TMPG) 2/3. There were 664 (71%) patients with residual ST elevation (ST-E) <2 mm. Ninety-day mortality and death/CHF/shock were lower in patients with TIMI flow 3 vs <3 (1.9% vs 6.2%, P = .002; 5.8% vs 10.4%, P = .044) and those with TMPG 2/3 vs 0/1 (2.0% vs 7.9%, P = .001; 6.0% vs 11.9%, P = .028). Patients with residual ST-E <2 mm had similar rates of mortality as those with ≥2 mm (2.3% vs 3.3%, P = .374) but lower rates of death/CHF/shock (5.2% vs 9.6%, P = .013). After multivariable adjustment, only post-PCI TMPG 2/3 was significantly associated with survival ( P = .001), whereas residual ST-E ( P = .606) and post-PCI TIMI flow grade ( P = .086) were not. Conversely, residual ST-E ≥2 mm ( P = .012) rather than angiographic reperfusion was associated with the composite of death/CHF/shock events. Conclusion Angiographic and electrocardiographic estimates of reperfusion with primary PCI in ST-segment elevation myocardial infarction provide different and complementary predictions of morbidity and mortality.