Although glycoprotein (GP) IIb/IIIa inhibitors are recommended for patients with unstable angina and non–ST-segment elevation myocardial infarction who undergo percutaneous coronary intervention (PCI), the American College of Cardiology/American Heart Association guidelines do not specify optimal timing for their initiation. We compared patient characteristics and clinical outcomes in 30,830 patients with non–ST-segment elevation myocardial infarction included in the CRUSADE initiative (January 2001 to December 2004) who underwent PCI with upstream (>1 hour before PCI) or periprocedural use of GP IIb/IIIa inhibitors. GP IIb/IIIa inhibitors were administered upstream in 43% of patients versus periprocedurally in 57%. Time from arrival to PCI was longer for patients who received GP IIb/IIIa inhibitors upstream (median 25.6 hours) compared with periprocedurally (18.2 hours). Unadjusted incidence of in-hospital death or reinfarction was lower with upstream GP IIb/IIIa inhibitor use (3.8% vs 4.3%, p = 0.046), but after adjusting for patient and hospital characteristics, this difference was not statistically significant. Treatment with upstream GP IIb/IIIa inhibitors was associated with a lower incidence of unadjusted death or reinfarction in patients who underwent PCI <12 hours from hospital arrival. In conclusion, in this observational analysis, overall ischemic outcomes were similar between the 2 groups, but clinical trials are needed to solve the controversy over optional timing of GP IIb/IIIa inhibitor use.