Abstract: 125Ⅰ-labelled "defibrinase" had been prepared by oxidant-chloroamine T.Drug is given in different ways:Subcutaneous,muscle,intravenous injection,the cases of distribution and excretion in different times in internal organs and in blood of rats,mice,and rabbits had been observed.It had been found that the time which 125Ⅰ-labelled "defibrinase" needed to eliminate half of its radioactive dose from blood in the animals was three of four hours.The times when radioactive distribution reached to its highest point by different ways of giving drugs in each internal organs of animals were varied;six hours for subcutaneous injection,three hours and one hours for muscl and intravenous injection.Compared with other parts of the accumulation of the 125Ⅰ-labelled "defibrinase" in kidney is the highest.The large quantity of by-products of "defibrinase metabolids" is eliminated from urine by kidney,the rest of it by excrements.