Regional brain volumes derived from magnetic resonance imaging (MRI) scans from 10 youths with early onset conduct disorder and 10 healthy controls matched for age, sex and handedness were compared to determine whether prefrontal or temporal lobe brain volumes differed in the two groups. Right temporal lobe and right temporal gray matter volumes were significantly reduced in subjects with conduct disorder compared with controls. Prefrontal volumes in subjects with conduct disorder were 16% smaller than in controls, but the difference did not reach statistical significance. Early onset conduct disorder without substance abuse comorbidity was also significantly associated with smaller right temporal gray volumes. Further investigation of both the temporal and frontal localizations of the pathophysiology of early onset conduct disorder is warranted in larger samples.