The purpose of investigation is the study of combined influence of gamma-radiation (137Cs, 1.25 Gy during 20 days) and mercazolyl (20 mg/100 ml drinkable water) in utero on the intellectual state of rats in the postnatal ontogenesis. It was shown, that antenatal separate influence both of gamma-radiation and mercazolyl induced the delay of intellectual development in 2 and 7 months age. The combined influence of these factors induced essential increase observed effect. There is a party of the conditioned reflex activity in 7 month age.