We determined the timing of ischemic complications within 30 days after percutaneous coronary intervention (PCI) in patients enrolled in the Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial. Complications (death, myocardial infarction [MI], target vessel revascularization) occurred in 178 of 2064 patients (8.6%) within 30 days. More than 85% of complications occurred within the 24 hours following randomization, with the greatest risk hazard at 12-18 hours. Unexpectedly, 31% of patients who ultimately met criteria for an endpoint MI within 24 hours of PCI had completely normal CK-MB concentrations at the first 6-hour measurement. There was no rebound increase in events after cessation of eptifibatide. Treatment benefit persisted to 30 days. Post-procedural MI is often not detected until greater than or equal to 12 hours after PCI. Treatment with a glycoprotein IIb/IIIa inhibitor is the only modifiable parameter that reduces the risk for early ischemic complications.