Structural neuroimaging studies done by means of magnetic resonance imaging (MRI) have provided important insights into the neurobiological basis for autism. The aim of this article is to review the current state of knowledge regarding structural brain abnormalities in autism. Results of MRI studies dealing with total brain volume, the volume of the cerebellum, caudate nucleus, thalamus, amygdala, hippocampus and the area of the corpus callosum are summarized. Existing research suggests that autistic individuals have larger total brain, cerebellar and caudate nucleus volumes; however, the area of the corpus callosum is reduced. Results of studies involving the amygdala and hippocampus volume in autistic subjects remain inconsistent and no changes have been detected in thalamic volume.