In this paper the effects of Cellular immunity reaction after whole Body irradiation of dogs were examined by counting. T. B cells in peripheral blood and determining function of incorpration of ,3,H-TdR.,1. Effects of Cellular immunity of dogs after ,60,Co whole body irradiation with lethal dose.,The dogs after irradiation were sampled on the 1 st, 3 rd, 6 th, 10 th and 13 th day, respectively, and compared with the dogs without irradiation. The results showed that the number of T. B cells in irradiation group declined rapidly from the 1 st day after irradiation. It was decreased to 38.5% and 28.5%. The incorporation function of ,3,H-TdR was suppressed seriously. The stimulation index reached to zero value on the 6 th day after irradiation and began to recover from the 10 th day after irradiation.,2.The effects of cellular immunity of dogs after treatment with 2 and 350 times the maximum permisible dose of thorium.,The results showed that there was no significant difference of cellular immune function between the large dosage group and control group, but the cellular immune function in the small dosage group was three times as large as that in control group. This indicated that the small dosage of irradiation might stimulate the immune proliferation of animals.