At least 5% of patients who undergo percutaneous coronary intervention have evidence of a periprocedural myocardial infarction. This review examines the clinical, diagnostic, and therapeutic implications of this diagnosis, as well as its implications for clinical trials. Approximately 1.5 million patients undergo percutaneous coronary intervention (PCI) in the United States every year. 1 Depending on local practices and the diagnostic criteria used, 5 to 30% of these patients (75,000 to 450,000) have evidence of a periprocedural myocardial infarction. 2 , 3 At the higher estimate, the incidence of these events is similar to the annual rate of major spontaneous myocardial infarction. 1 Thus, many cardiologists and internists are likely to encounter patients with coronary artery disease who have sustained a periprocedural myocardial infarction. However, the clinical significance of these events and their management remain a matter of considerable controversy and uncertainty . . .