Effects of pretreatment of mouse with low doses of internally deposited147Pm on the mutagenicity of both the bone marrow lymphocytes and the spermatoblasts induced by subsequent high dose of internally deposited 147Pm were studied.Kunndng male mice were injected from the tail vein with low doses of “’Pm(NO.).Of 0.37, 3.7 and 37Bq/g body weight. Three dabs later the mice were injected witha high dose of 147Pm(NO.)3 of 18.5 kBq/g body weight. The animals were sacrificedat 24h after the high dose injection. The results show that the bone marrow lymphocytes and the spermatoblasts pre-exposed in fido to low doses of 147Pm can producean adaptive response. The radioadapted cells had a resistance to the mutagenicity induced by the subsequent high dose of 14’Pm, that is, the proportion of both the bonemarrow lymphocytes containing ndcronuclei and the sperm shape abnormalities wassignificantly lower than those for the pure high dose group (P <0.01). In addition, theinduction of the adaptive response of the cells possesses the different dose ranges forthe different biological parameters. The 147Pm dose ranges of the adaptive responseare 0.37-3.7 and 0.37-37 Bq/g body weight for the frequency of micronucleated bonemarrow lymphocytes and abnormal sperrnst respectively. Effects of pretreatment of mice with low doses of internally deposited147Pm on the mutagenicity of both the bone marrow lymphocytes and the spermatoblasts induced by subsequent high dose of internally deposited 147Pm were studied. Kunndng male mice were injected from the tail vein with low doses of ” Three dabs later the mice were injected witha high dose of 147Pm (NO.) 3 of 18.5 kBq / g body weight. The animals were sacrificedat 24h after the high dose injection. The results show that the bone marrow lymphocytes and the spermatoblasts pre-exposed in fido to low doses of 147Pm can producean adaptive response. The radioadapted cells had a resistance to the mutagenicity induced by the subsequent high dose of 14’Pm, that is, the proportion of both the bonemarrow lymphocytes containing ndcronuclei and the sperm shape abnormalities wassignificantly lower than those for the pure high dose group (P <0.01). In addition, the induction of the adaptive res ponse of the cells possesses the different dose ranges forthe different biological parameters. The 147Pm dose ranges of the adaptive responseare 0.37-3.7 and 0.37-37 Bq / g body weight for the frequency of micronucleated bonemarrow lymphocytes and abnormal sperrnst respectively.