Background: Studies have shown that ticlopidine and clopidogrel in association with aspirin reduce the short- and long-term incidence of major adverse coronary events in patients undergoing stent implantation. Furthermore, clopidogrel seems to show a better side-effect profile than ticlopidine, and recent evidence supports its efficacy in long-term prevention in high-risk patients. Methods: From May 2002 to December 2003, 428 consecutive patients with 1st coronary event underwent a percutaneous coronary intervention (PCI) for non-ST elevation myocardial infarction. All patients received a glycoprotein IIb/IIIa inhibitor and were randomized in double-blind fashion to ticlopidine (500 mg/day) + aspirin or clopidogrel (75 mg/day) + aspirin before PCI. After 48– 72 h, PCI with stent implantation was performed and the treatment was continued for 6 months. Two groups were obtained. The clopidogrel group contained 214 patients (146 M/68 F), mean age 61.3 ± 11.8 years, and the ticlopidine group contained 214 patients (150 M/64 F), mean age 60.7 ± 10.5 years. A protocol that included clinical follow-up at 1, 3 and 6 months was used. Results: Both groups were comparable in baseline characteristics. We observed 14 cases of non-cardiac side effects in the clopidogrel group in the first 30 days after discharge. The ticlopidine group showed 20 non-cardiac side effects (not significant). None of the patients died during the follow-up. Both groups were similar in number of diseased vessels and number of stents. During follow-up (180 days), 48 patients from the clopidogrel group and 44 from the ticlopidine group showed reocclusion in vessels treated with percutaneous transluminal coronary angioplasty (p value not significant). In addition, we observed that reocclusion was mostly evidenced in the first 90 days (44 from the clopidogrel and 40 from the ticlopidine group). In the remaining time (90 days), we observed only 4 cases of reocclusion from the clopidogrel and 4 cases from the ticlopidine group. Conclusion: Our data suggest that ticlopidine or clopidogrel associated with aspirin determine similar effects.