The brain of a 7-year-old girl with developmental dysphasia who died of complications of infectious mononucleosis was examined grossly and histologically. The neuropathological studies revealed atypical symmetry of the plana temporale and a dysplastic gyrus on the inferior surface of the left frontal cortex along the inferior surface of the sylvian fissure. These anomalies are likely related to midgestation, the period of neuronal migration from the germinal matrix to the cerebral cortex, and are consistent with a neurodevelopmental cause of developmental dysphasia.