Objectives. The purpose of this study was to compare the outcome of primary percutaneous transluminal coronary angioplasty for acute myocardial infarction (MI) when performed with or without the platelet glycoprotein IIb/IIIa antibody, abciximab. Background. Abciximab improves the outcome of angioplasty but the effect of abciximab in primary angioplasty has not been investigated. Methods. Data were collected from a computerized database. Follow-up was by telephone or review of outpatient or hospital readmission records. Results. A total of 182 consecutive patients were included; 103 received abciximab and 79 did not. The procedural success rate was 95% in the two groups. At 30-day follow-up, the composite event rate of unstable angina, reinfarction, target vessel revascularization and death from all causes was 13.5% in the group of patients who did not receive abciximab, 4% (p < 0.05) in the abciximab group and 2.4% (p < 0.05) in the subgroup of patients (n = 87) who completed the 12-h abciximab infusion. At the end of follow-up (mean 7 +/- 4 months), the composite event rate was 32.4%, 17% (p < 0.05) and 13.1% (p < 0.01) in these three categories respectively. Abciximab bolus followed by a 12-h infusion was an independent predictor of event-free survival, in a Cox proportional hazards model (relative risk 0.49; 95% confidence interval 0.24 to 0.99; p < 0.05). Conclusions. Abciximab given at the time of primary angioplasty may improve the short- and medium-term outcome of patients with acute MI, especially when a 12-h infusion is completed. (J Am Coil Cardiol 1998;32:1996-2002) (C) 1998 by the American College of Cardiology.