Three groups of men, 50 with manifest ischemic heart disease (IHD), 50 with risk indicators of IHD and 50 healthy men, were examined for ventricular arrhythmias with 24-hour Holter monitoring during normal work and home life. Ventricular arrhythmias were most frequent in the IHD, intermediate in the risk and least frequent in the control group. Multiform ventricular ectopic beats, but no other qualitative characteristic significantly discriminated the three groups. The following risk indicators were associated with ventricular arrhythmias: ageing, cardiac enlargement and smoking. The results suggest that long-term ECG monitoring may be of value for the detection of ventricular arrhythmias not only in men with clinical IHD, but also in those with merely risk indicators.