Left over right asymmetries in volume have been found in two subareas of the medial prefrontal cortex (PFC), and a right over left in the orbital PFC. The asymmetries change during development, indicating differential growth rates for left and right PFC parts. The asymmetry of the medial PFC reached significance from day 10 until day 18 and at day 90. The asymmetry of the orbital PFC reached significance from day 30 until day 60. At day 90 no significant asymmetry is demonstrated in this part of the PFC. A significant sexual dimorphism was demonstrated for the dorsal agranular insular subarea (AId) in the orbital PFC.