It is generally accepted that ventricular arrhythmias represent a predictor of prognosis after myocardial infarction, and that their impact on the increase of risk is especially unfavourable when associated with myocardial ischaemia or reduced left ventricular function. The aim of the study was to assess the significance and contribution of noninvasive ECG methods in detection of risk due to sudden cardiac death in Q postmyocardial infarction patients. Two-hundred and seventy patients were examined by exercise testing which in 5.2% of cases revealed couplet ventricular extrasystoles and 0.8% yielded non-sustained ventricular tachycardia. 24-hour-Holter ECG recording was performed in 168 patients (19.0% of couplet ventricular extrasystoles, 9.0% of non-sustained and 0.6% of sustained ventricular tachycardia respectively), and 300 patients were examined by late ventricular potentials analysis with a result of 25% positive cases. During 3 years of follow-up, 20 out of 300 patients (6.7%) died suddenly; in this group late ventricular potentials occurred significantly more frequently than in survivors. Exercise testing plays a major role in the detection of myocardial ischaemia, while Holter recording and signal averaging for detection of late ventricular potentials are important in noninvasive diagnosis of ventricular arrhythmias. Their combination with other ECG techniques (heart rate variability, QT dispersion) and determination of global function of the left ventricle may help to identify the group of patients in whom subsequent electrophysiological study is indicated in order to determine the optimal therapy for mortality reduction after myocardial infarction. (Fig. 5, Tab. 3, Ref. 20.)