Heart rate variability (HRV) is used for stratification of risk for sudden death due to malignant arrhythmias after myocardial infarction (MI). HRV was analysed in 221 consecutive patients who underwent cardiac rehabilitation within 4 weeks to 3 months after acute MI. Patients with MI had significantly lower all measures of HRV in comparison with control group (SDNN 125 +/- 37 vs. 152 +/- 38 ms, p < 0.0001). Patients with anterior MI had lower overall HRV (SDNN 116 +/- 35 vs. 132 +/- 37 ms, p = 0.001) and higher heart rate than those with inferior MI. Diminished HRV persists 3 months after MI. It is assumed that patients with anterior MI had higher potential risk of malignant arrhythmias and sudden death than those with inferior MI.