OBJECTIVE: Morphological indications of abnormal circuitry have been detected in the prefrontal neuropil of patients with schizophrenia. The authors tested the hypothesis that schizophrenia is associated with smaller dendritic field size in layer V pyramidal neurons in the prefrontal cortex. METHOD: Tissue from area 10 with a mean postmortem interval of 5.7 hours was obtained from 15 subjects with chronic schizophrenia and 18 normal comparison subjects. After Golgi impregnation, basilar dendritic field size was estimated for layer V pyramidal neurons by ring intersection analysis. RESULTS: The schizophrenia subjects had 40% fewer total ring intersections per neuron than comparison subjects. Smaller basilar dendritic field size was evident in proximal and distal branches. CONCLUSIONS: These results indicate that abnormal dendritic outgrowth or maintenance contributes to reduced neuropil and prefrontal connectivity in schizophrenia. Short postmortem intervals and resulting high tissue quality suggest that these dystrophic changes reflect schizophrenia pathology rather than postmortem artifact.