From March 1986 through October 1987, elective diagnostic coronary angiography was performed in 1,542 consecutive patients. Among them, silent myocardial ischemia was investigated based on the histories in their medical questionnaires, the results of exercise stress tests and the presence of significant coronary artery stenosis. Exercise-induced silent myocardial ischemia was documented only in 3% in the non-infarction group, and in 2.1% of those with significant coronary stenosis. However, asymptomatic post-infarction patients comprised 33%. With regard to the extent of coronary artery disease in the non-infarction group, one-, two- and three-vessel disease accounted for 42%, 29% and 29%, respectively (NS). However, one-vessel disease was predominant among the asymptomatic post-infarction patients (p < 0.01). Among the non-infarction group, those with asymptomatic coronary stenosis had a relatively high incidence of diabetes mellitus (p < 0.01), but such a difference was not significant among the asymptomatic post-infarction patients. Among the post-infarction group, many of those who had chest pain during exercise showed redistribution on exercise thallium scintigraphy. Angioplasty was performed in most of the patients in the asymptomatic group, but its long-term effects are yet unknown.