Present study carried out to investigate the effect of letrazol on congenital malformation, and histopathological change in mice fetus  brain, 32 pregnant albino mice were divided into 3 equal groups then letrazol were administrated by cavage in different concentration (2.5,5,7) mg/kg at7^th to the 18^th day of gestation. The results showed That malformation reach to100%at 7mg/kg body weight it represented as a cleft lip exophthalmia eye, lose eyes shortening of the fore limbs, the tail malformation, Microscopically histological lesions of fetus brain shows an infiltration of inflammatory cells, necrosis and vocal degeneration.