Previous research has revealed a lack of planum temporale (PT) asymmetry in adults with autism. This finding is now extended to children and adolescents with the disorder. MRI scans were obtained from 12 children with autism and 12 gender, handedness and age-matched comparison participants. The volume of gray matter in the PT and Heschl's gyrus (HG) in both hemispheres was measured. PT volume was larger in the left hemisphere than in the right in the comparison, but not the autism group. This specifically reflected reduced volume of the left PT in the autism group. There were noted differences in the overall morphological appearance of the right Sylvian fissure in the autism group, but no volumetric difference in the right PT. No differences in HG volumes were observed between the two groups. Lack of PT asymmetry may suggest an early neurodevelopmental disturbance in autism.