Due to their neurotoxic effects, acute heavy metal exposures cause well-known clinical symptoms of intoxication in both animals and man. The aim of the present study was to investigate the functional changes of the central nervous system caused by relatively high heavy metal doses, by means of analyzing some EEG parameters, in acute experiments. Male Wistar rats were orally treated by gavage with 1600.0 and 3200.0 mg/kg lead (in form of lead acetate) or 8.0 and 16.0 mg/kg mercury (in form of mercury chloride). The EEG of the anesthetized rats was recorded with silver electrodes placed on the primary somatosensory, visual and auditory centres at 24, 48, 72 hours and 7 days after the treatment. The analysed parameters were: mean amplitude, mean frequency, EEG index and the power spectrum of the frequency bands. The data showed that both doses of the above metals caused considerable, dose- and time-dependent changes of the measured parameters of EEG.The importance of our results is emphasized by the fact that the functional consequences of the population's heavy metal exposure are not yet fully understood.