Results from previous studies evaluating the electroencephalograms (EEGs) of infants born to alcoholic mothers suggest that the neonatal EEG may be a sensitive measure of prenatal ethanol exposure. Few studies, however, have examined EEG records of adolescent children with fetal alcohol syndrome (FAS). The present study investigated the resting EEG recordings of 18 matched triads of FAS, Down syndrome, and normal control subjects. Significant reductions in mean power of the alpha frequencies (7.5-12 Hz) were seen for both clinical groups, however, each syndrome appeared to have distinct EEG spectral distributions. Down syndrome children overall had diffuse EEG slowing while the EEG records of the FAS children showed reduced power, particularly in the alpha frequencies in the absence of significant slow activity. In the Down syndrome children, significant decreases in alpha power was seen in posterior cortical regions, whereas FAS children were more affected in the left hemisphere. This study suggests that certain EEG variables may be helpful in characterizing the neurophysiology of FAS.