BACKGROUND: Coronary stenting with use of heparin, aspirin, and ticlopidine for thromboprophylaxis is performed in more than 500,000 patients per year worldwide. We did a randomised controlled trial to assess the role of platelet glycoprotein-IIb/IIIa blockade for use in elective stenting. METHODS: At 63 hospitals in the USA and Canada, 2399 patients with ischaemic heart disease and suitable coronary-artery lesions were randomly assigned stenting plus placebo (n=809), stenting plus abciximab, a IIb/IIIa inhibitor (n=794), or balloon angioplasty plus abciximab (n=796). The primary endpoint was a combination of death, myocardial infarction, or need for urgent revascularisation in the first 30 days. All patients received heparin, aspirin, and standard pharmacological therapy. FINDINGS: The primary endpoint occurred in 87 (10.8%) of 809 patients in the stent plus placebo group, 42 (5.3%) of 794 in the stent plus abciximab group (hazard ratio 0.48 [95% CI 0.33-0.69] p<0.001), and 55 (6.9%) of 796 in the balloon plus abciximab group (0.63 [0.45-0.88] p=0.007). The main outcomes that occurred less with abciximab were death and large myocardial infarction--7.8% in the placebo group, 3.0% for stent plus abciximab (p<0.001), and 4.7% for balloon angioplasty plus abciximab (p=0.01). Major bleeding complications occurred in 2.2% of patients assigned stent plus placebo, 1.5% assigned stent plus abciximab, and 1.4% assigned balloon angioplasty plus abciximab (p=0.38). INTERPRETATION: Platelet glycoprotein-IIb/IIIa blockade with abciximab substantially improves the safety of coronary-stenting procedures. Balloon angioplasty with abciximab is safer than stenting without abciximab.