Twenty birds of Hyline hen aged 13 months were used in this experiment. 80 uci. of Radioactive-iodine^(131) were administered to each laying hen in the purpose of determination of the uptake and distribution as related to the process of time, of the every parts of eggs. The I^(131) uptake rate of yolk, white and shell of the eggs and the excretion rate in the feces was measured at ½, 1½, 2½, 3½, 4½, 5½, 6½, 7½, 8½, 9½, and 10½ days after the administration of I^(131). The results obtained are as follows; 1. The I^(131) uptake rate in the yolk was lowest at ½ day with 6×10^(-4)±0.09×10^(-4)% and was highest with 1816×10^(-4)±122.7×10^(-4)% at 4½ days, thereafter gradually decreased (P$lt;0.01). 2. The I^(131) uptake rate in the white was highest at ½ day with 145×10^(-4)±4.7×10^(-4)% and then decreased significantly(p$lt;0.01) as time elapses, and its decreasing rate was relatively slow during the ½ day and 3½ day, the 7½ day, and 10½ day. 3. The I^(131) uptake rate in egg-shell was highest at ½ day with 129×10^(-4)±1.1×10^(-4)±% and lowest at 10½ days with 20×10^(-4)±1.0×10^(-4)±%, showing the decreasing significance with p$lt;0.01 and decreased gradually as the process of time. 4. The I^(131) excretion rate in the feces decreased gradually(p$lt;0.01), and the decreasing rate was fast until 3½ days and slow after then. 5. The I^(131) uptake rate in the every parts of eggs and excretion rate in the feces showed the high significance(p$lt;0.01) as compared with the each observation time anti were rot significant among the white. shell and feces except egg-yolk.