92 infants were studied in order to determine the prognostic value of bioelectric brain maturity assessment during newborn period. Psychomotor development was followed up until infants were at least one year old. Infants with abnormal follow-up examination findings showed a statistically significant retardation of "EEG-maturity" in comparison with infants who developed normally. The more unfavourable the psychomotor development was, the more immature was the EEG-pattern. The prognosis of 6 infants whose "EEG-maturity" was extremely retarded (= 4 weeks immature) was severe; their follow-up examination revealed either definite pathological findings or severe cerebral damage. All newborns whose abnormal electroencephalogram recording did not allow assessment of "EEG-maturity" developed severe cerebral damage. Comparing the prognostic value of risk factors with the bioelectric brain maturity the last method proved to be more valuable. Especially in infants with perinatal hypoxia this method showed the highest prognostic value.