The frequency and distribution of risk factors of arteriosclerosis were determined in 405 patients with implanted cardiac pacemakers and compared with the corresponding results of patients with cardiac infarction. The most frequent risk factors were smoking (43,5%), hypertension (35,2%), and diabetes (34,3%) in males, hypertension (52,3%) and diabetes (49,7%) in females. The frequency of cardiac infarction was in average 19,5%. In the infarction group diabetes was lower in both sexes (23,5% and 35,8%), respectively), hyperlipoproteinemia and smoking were more frequent. From the different distribution of risk factors it is suggested, that coronary arteriosclerosis is not the most important etiologic factor in the development of bradycardic dysrhythmias. The higher percentage of diabetes in the pacemaker group could point to metabolic disturbances or specific diabetic vascular disease as harmful factors to the conduction system.