Abstract: I Nerve growth factor ( 125 I NGF) with more than 95% of radiochemical purity is prepared by chloramine T method.After iv and im injection of 125 I NGF,pharmacokinetics of NGF in mice is determined by SDS PAGE method. The results show that concentration time curves after iv injection are fitted to a 2 compartment model and those after im injection are fitted to a 1 compartment model. After iv injection of 25 μg/kg,the elimination half life ( t 1/2 (β) ) is 3.65 h. After im injection of 75,25,10,3.3 μg/kg, t 1/2(β) is 1.79,2.25,2.30,3.24 h,respectively. The mean plasma clearance (CLs) is 0.37 L/(h·kg), the appearance volume of distribution ( V d) is 1.18 L/kg and the mean residence time ( r) in mice is 2.78 h. The pharmacokinetics of 125 I NGF in mice is useful for clinical trial.