The purpose of the investigation is the study and analysis 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 physical developmental of the rats in the postnatal ontogenesis. It was shown, that antenatal separate influence both of gamma-radiation and mercazolyl induced the decrease of the strength endurance. The combined influence both of these factors induced essential decrease of the strength endurance.