Silent myocardial ischemia and ventricular arrhythmias were known to be independent risk factors in patients with coronary artery disease. This has become more important since the technique of Holter monitoring has been improved and has demonstrated a high incidence of silent myocardial ischemia in the majority of patients with coronary artery disease, as well as a close relation to the occurrence of sudden cardiac death. Unfortunately, prospective data on the interaction of both risk factors are missing. We therefore studied patients undergoing exercise-testing, percutaneous transluminal angioplasty and 24-h-Holter-monitoring to assess such an interaction. During exercise testing the total incidence of ventricular arryhthmias in patients with asymptomatic ST segment depression was 42%; 6% of patients had frequent ventricular arrhythmias, 6% had ventricular pairs, and 1% had ventricular tachycardia. The incidence was similar to patients with symptomatic ST depression, but was 3.2-times higher as compared to patients without ST segment depression. During 103 attempts of percutaneous transluminal angioplasty, in 26 patients ventricular arrhythmias occurred, the incidence of ventricular tachycardia was 1-3%. No difference was observed for symptomatic and asymptomatic attempts. In 36 patients with severe coronary stenosis (greater than 90%) 24-h-Holter-monitoring showed 145 episodes of myocardial ischemia with a total duration of 967 min; two-thirds of episodes were asymptomatic. The incidence was similar in patients with symptomatic and asymptomatic episodes of myocardial ischemia, but 30 to 50-times higher as compared to the interval with ischemia. In summary, episodes of myocardial ischemia have a higher risk of ventricular arrhythmias, however, there is no difference between symptomatic and asymptomatic myocardial ischemia.