Stents have revolutionized percutaneous coronary interventions (PCI), impacting on both acute and long-term results. However, despite improvements in stent design, stent deployment failure is not an unusual event. The aim of the present study was to assess the frequency and causes of stent deployment failure, as well as the outcome of these patients. Between 1997 and 2001, a total of 3,537 patients underwent stent-assisted PCI and delivery of 5,275 stents was attempted. In the majority of patients (118; 78.1%), stenting was performed as provisional; in the remaining 33 (21.8%) as a bailout procedure. A total of 175 (3.3%) stents in 151 (4.3%) patients failed. Failure to deliver the stent to the lesion site was the main cause in 139 patients (92%) and failure either to expand adequately the stent or premature disengagement of the stent from the balloon in only 12 patients (8%). Peripheral stent embolization occurred in 10 (0.3%) patients. Deployment of a different stent in place of the failed one was attempted in 122 patients and was successful in the majority (108; 88.5%). In-hospital major adverse cardiac events were observed in six patients (4%): three patients required emergency coronary artery bypass surgery, two had a myocardial infarction (MI), and one patient underwent urgent repeat coronary intervention. At a mean follow-up of 32.2 +/- 17.7 months, 22 major adverse cardiac event occurred in 17 patients (11.2%): 1 cardiac death, 3 patients had an MI, and 18 patients required target vessel revascularization. One-year event-free survival for the whole group was 91.2%. Patients with stent embolization did not have any major adverse cardiac or vascular events. Thus, the rate of stent deployment failure in our series was 3.3%, mainly due to failure to deliver the stent to the site. Another stent was successfully deployed in the majority of cases and these patients had favorable short- and long-term outcomes.