Up to 20% of patients undergoing successful coronary angioplasty have been shown to have a mild elevation of creatine kinase-MB (CK-MB). The purpose of this study was to investigate the relationship between clinical and angioplasty procedural variables and circulating markers for cardiac injury. We measured both CK-MB and totally cardiac-specific troponin inhibitory protein (Tn-I) in 22 patients immediately before and at an average time of 10 h 36 min following successful angioplasty. Of these patients 16 had stable angina, six had unstable angina and none had recent myocardial infarction. Four patients had minor complications associated with the procedure (prolonged chest pain, limited coronary artery dissection) but none of these patients had increases in either CK-MB or Tn-I. In two patients there was a mild increase in enzyme-activity assayed CK-MB but none of the 22 patients had significant elevation of mass-assayed CK-MB or cardiac-specific Tn-I. This study supports the view that no significant myocardial damage occurs as a result of successful coronary angioplasty irrespective of the stability of the coronary artery disease. This study confirms the known discrepancies between results obtained by immunoassay and immunoinhibition enzyme assay, due to the false-positive results which can be yielded by the latter technique.