To clarify factors affecting the prevalence of ventricular premature contraction (VPC) in patients with stable ischemic heart disease, daily profiles of VPC prevalence were studied in 92 patients using continuous 24-hour electrocardiographic recordings. VPCs in patient groups with effort angina and inferior infarction showed similar daily profiles. However, a significant relationship between VPC prevalence and heart rate was observed in inferior infarction group, while patients with resting angina exhibited another relationship between the two parameters. Higher prevalence rate of VPCs in the early morning in patients with resting angina suggested the contribution of cardiac autonomic nerve activity to the increased frequency of VPCs, while constant frequency of VPCs during the day in anterior infarction group provided no influences on heart rate, effort, and autonomic nerve activity on the VPC prevalence. Age, sex, left ventricular ejection fraction, and nitrates and diltiazem used for the treatment of angina pectoris did not affect the daily profile of VPC prevalence in any patient groups. These results indicated that the clinical and pathophysiological differences of ischemic heart disease, even in stable patients, showed the different distribution of VPC prevalence within a day which is due, in part, to the varied activities of cardiac autonomic nerves.