Peri-procedural myocardial infarction (MI) is a not infrequent complication of percutaneous coronary intervention (PCI), but conflicting information exists regarding incidence and prognostic impact of this event. We investigated frequency, causes, predictors, and clinical relevance of peri-procedural MI, using a large database. We pooled individual patient-level data from 11 PCI studies in which peri-procedural creatine kinase-MB mass was routinely measured and mortality data were prospectively collected. Among 23 604 patients from 11 studies, 1677 {7.1% 95% confidence interval (CI) 6.8-7.5%} had peri-procedural MI. The most common mechanism of peri-procedural MI was side-branch occlusion. Independent predictors of peri-procedural MI were older age, female gender, diabetes, hypertension, renal dysfunction, multivessel disease, left anterior descending artery disease, left main disease, bifurcation lesion, long lesion, drug-eluting stents, and number of stents. Follow-up varied from 1 year to 5 years. In a crude analysis, patients with peri-procedural MI had significantly a higher risk of mortality than those without peri-procedural MI hazard ratio (HR) 1.47; 95% CI 1.24-1.74. After adjustment for baseline covariates, peri-procedural MI was associated with an increased risk of mortality (HR 1.20; 95% CI 1.04-1.39). Among patients undergoing PCI, the occurrence of peri-procedural MI measured by CK-MB mass assay was ~7%, and more than half of cases were associated with side-branch occlusion. Several higher risk patients, lesions, and procedural characteristics were independent predictors of peri-procedural MI. Peri-procedural MI was associated with an increase in mortality.