Heart rate variability (HRV) reflects periodic changes taking place in heart rhythm, which are controlled by the autonomic nervous system (ANS) and external factors. The aim of the present study was to assess the relationship between HRV and the level of intelligence using the Raven Advanced Matrices Test in 95 men (mean age 41.6 +/-3.7 SD yr) who experienced myocardial infarction during two years preceding the psychophysiological examination. HRV was analyzed from the EEG signal recordings in the time and spectral domains. It was found that post-myocardial infarct men of the higher than average intelligence had significantly increased HRV; the finding was reflected in the analysis of both time and frequency domains. Although both sympathetic and parasympathetic components showed an increase in the frequency domain, the former did disproportionately more, achieving substantial predominance. The results indicate that active mental processes and attitude, linked to a higher intelligence level, might be a beneficial prognostic marker, as is higher HRV, for the overall post-infarction cardiac mortality and for return of such subjects back to normal life. The corollary is that the assessment of IQ in post-infarction patients seems a simple screening method that may help presage the health and social course the patient takes.