OBJECTIVE: Neurodevelopmental models of schizophrenia imply that a more severe early brain lesion may produce earlier onset of psychotic symptoms. The medial temporal lobes have been proposed as possible locations for such a lesion. The authors tested this hypothesis in a group of children and adolescents with childhood-onset schizophrenia who had severe, chronic symptoms and who were refractory to treatment with typical neuroleptics. METHOD: Anatomic brain magnetic resonance imaging scans were acquired with a 1.5-T scanner for 21 patients (mean age=14.6 years, SD=2.1) who had onset of schizophrenia by age 12 (mean age at onset=10.2, SD=1.5) and 41 normal children. Volumes of the temporal lobe, superior temporal gyrus, amygdala, and hippocampus were measured by manually outlining these structures on contiguous 2-mm thick coronal slices. RESULTS: Patients with childhood-onset schizophrenia had significantly smaller cerebral volumes. With no adjustment for brain volume, no diagnostic differences were observed for any temporal lobe structure. Unexpectedly, with adjustment for total cerebral volume, larger volumes of the superior temporal gyrus and its posterior segment and a trend toward larger temporal lobe volume emerged for the patients with schizophrenia. These patients lacked the normal (right-greater-than-left) hippocampal asymmetry. CONCLUSIONS: These findings do not indicate a more severe medial temporal lobe lesion as the basis of very early onset schizophrenia.