BACKGROUND AND OBJECTIVES: The purpose of the study was to evaluate the usefulness of cardiac troponin as a marker for the detection of minor myocardial injury following percutaneous coronary interverntion (PCI). SUBJECTS AND METHODS: In 79 patients who underwent successful PCI under the diagnosis of stable angina, serum creatinine kinase MB isoenzyme (CK-MB), cardiac troponin T (cTnT), and cardiac troponin I (cTnI) were measured before and at 6, 12 and 24 hours after PCI, and the angiographic findings and procedural characteristics of PCI were compared between the elevated and the normal enzyme groups. RESULTS: Abnormal values of one or more markers following PCI were observed in 17 patients (22%) ; 11 after stenting and 6 after balloon angioplasty alone. The frequency of abnormal cTnI levels was 19% and was significantly higher than that of CK-MB (6%, p < 0.01). No significant differences in target vessel number, target artery, ACC/AHA type, TIMI flow, stenting, time and number of ballooning, maximal inflation pressure or balloon diameter and length were observed between the two groups. Small side branch occlusions developed in 23% of the elevated enzyme group and in 3% of the normal enzyme group. CONCLUSION: Minor myocardial injury can be detected by cTnI and is observed frequently in patients with stable angina following PCI. A small side branch occlusion is related with elevated cTnI.