The activities of cytochrome oxidase (CYO) and succinate dehydrogenase (SDH) in brains of progeny of rabbits treated with dichlorvos (DDVP) 6 mg/kg/day during last ten days of pregnancy were investigated. Biochemical estimation of mitochondrial fraction of the brain tissue and the histochemical studies of fresh cryostat slices were carried out in 1, 8 and 16 day old rabbits. In comparison with control animals the decrease in CYO and SDH activity and the disturbances in "enzymatic maturation" rythm were observed in progeny of rabbits submitted to treatment with DDVP. In neuropil the changes were more pronounced than in pericarium of the nerve cells. In the brain structures which are sensitive to the metabolic disturbances (Ammon horn) SDH activities decreased.