Coronary stent implantation has become an accepted treatment for selected patients but the long-term outcome after stent implantation has not been investigated in a large unselected population. This study reports clinical and angiographic results after coronary stent implantation in a consecutive group of 1000 patients treated between November 1989 and June 1994. A total of 2012 stents were implanted in 1216 lesions. The anticoagulation regimen after successful stenting was abolished in the last 499 patients, treated with aspirin and ticlopidina. Complex lesions (type B2, type C lesions and chronic total occlusions) were less frequent in the group with anticoagulation (67%, 355/529 lesions) than in the group without anticoagulation (76%, 485/641; p < 0.01). Vessel size was also significantly smaller in the group with no anticoagulation (3.21 +/- 0.50 mm vs 2.89 +/- 0.70 mm; p < 0.001). Procedural success was achieved in 96% of cases. Major complications occurred in 49 pts, including death (1%), emergency bypass surgery (2.7%), and myocardial infarction (2.1%). Subacute stent thrombosis, observed in 2.6% of the patients treated with anticoagulation, decreased to 1% in the last 499 patients receiving only antiplatelet drugs after high pressure stent expansion controlled with intravascular ultrasound (p < 0.05). Angiographic follow-up was obtained at a mean interval of 6.6 +/- 3.0 months in 718 patients (75% of the eligible candidates). The global restenosis rate (greater than 50% diameter stenosis) was 22%, with no statistically significant difference in patients with and without anticoagulation after stenting. Clinical follow-up was available in 890 patients at a mean interval of 14 +/- 17 months. Late cardiac events occurred in 251 patients and included: 159 repeat coronary angioplasties for restenosis (20%), 114 coronary angioplasties for de novo lesions (10%), 33 elective by-pass surgery operations (3.7%) and 42 late deaths (4.7%). At the most recent follow-up there were 719 pts (81%) free of anginal symptoms, including patients having repeat angioplasty for restenosis or disease progression. Coronary stenting has a low incidence of procedural complications and high-pressure ultrasound guided implantation has drastically reduced the risk of subacute thrombosis. Repeat procedures due to restenosis remain the most important limitation of the technique and do not seem to be affected by evolving technique and operator experience.