ObjectiveTo probe the laws of the cross-adapting respons e induced by low dose radiation and low concentration mitomycin C.MethodsThe human lymphocytes,bone marrow cells of mice w ere treated by low dose X-ray or low concentration mitomycin C before treated b y high dose X-ray or high concentration mitomycin C.Some targets were observed,s uch as chromosome aberration of human lymphocytes,bone marrow cells of mice,micr onuclear(MN),sister chromatied exchange(SCE).ResultsThe targets of above all appeared cross-adapt res ponse.ConclusionCross-adapt response can be inducd by low dose radiation or by low concentration mitomycin C not only in vivo but also i n vitro.