Background The antithrombotic benefit of the conventional treatment with coumadin after coronary stenting is limited by bleeding complications. However, the superiority of an antiplatelet therapy with aspirin alone compared with coumadin plus aspirin has not been proven by randomized studies. The efficacy and safety of treatment with aspirin alone in comparison to coumadin plus aspirin were evaluated in this randomized study. Methods Out of 164 patients aged 59.7 ± 9.2 years, 79 patients were randomly assigned to receive 100 mg aspirin daily (group A) and 85 patients randomly assigned to coumadin plus aspirin (group CA) after provisional coronary stenting with a high-pressure technique. The primary end point was defined as the absence of death, subacute closure of the target vessel, myocardial infarction, urgent coronary bypass surgery, repeated coronary angioplasty, and peripheral vascular complications requiring transfusion or surgery. High-pressure inflation technique was used, but ultrasound guidance was not. Results During hospitalization (median 8 days), 135 patients (82.3%) were free of events (A, 84.8%; CA, 80.8%; P = .42). Eleven (6.7%) subacute closures occurred (A, 10.1%; CA, 3.5%; P = .09); 2 of them were lethal in the aspirin group. Emergency bypass surgery was performed in 1 patient in each group. Peripheral vascular complications were observed in 13 patients (7.9%) (A, 1.3%; CA, 14.1%; P < .01). At 3-month follow-up, 15 (9.1%) elective revascularization procedures (A, 7.6%; CA, 10.6%; P = .51) were performed. Conclusion Aspirin alone at the low dose of 100 mg administered or the combination of coumadin and aspirin after high-pressure coronary stenting does not prevent adverse clinical events when ultrasound guidance is not used. (Am Heart J 1999;138:663-9.)