The appearance of a new coronary artery lesion is important in patients with acute myocardial infarction or late coronary artery bypass grafting surgery, which sometimes lead to cardiac death. We studied coronary angiograms of 1,098 patients with coronary artery disease (from 1985 to 1996) and found new lesions in 94 patients (male 74, female 20; mean age 61.6 years). Mean observation period of all 1,098 patients was 50.1 +/- 30.4 months, and that of patients with new lesions was 73.2 +/- 31.2 months. Clinical findings of the 94 patients were acute myocardial infarction (n = 28), recurrent angina (n = 56), and silent ischemia (n = 10). The appearance of a new coronary lesion was found in 2.4% (1992), 1.9% (1993), 2.3% (1994), 1.7% (1995) of all patients with ischemic heart disease per year. The new lesions were found more often in patients with non-significant stenotic lesions (n = 74) than in patients with lesions of > or = 50% stenosis (n = 20). Complex lesions were found in 56% of the recurrent angina group, and in 22% of the silent ischemia group. In our study, the rate of appearance of new coronary artery lesions was much lower than in Europe or the United States of America. These results require careful consideration for coronary revascularization procedures in Japanese patients.