The objectives of this study were to investigate cortical development and hemispheric asymmetry in abused children. Fifteen hospitalized children (mean age 10.7 +/- 2.5 years) with severe physical or sexual abuse and 15 normal children (10.1 +/- 3.1 years) were studied with quantitative EEG. Abused children had higher levels of left hemisphere coherence and a reversed asymmetry, with left hemisphere coherence significantly exceeding right hemisphere coherence. Left hemisphere coherence decreased more rapidly across electrode distance in normal subjects, suggesting that increased left coherence in abused patients stemmed from a deficit in left cortical differentiation. These findings support the hypothesis that early severe abuse may have a deleterious effect on brain development.