The study was undertaken to evaluate the protective effect of epinephrine on renal radiation injury. For theexperiment, 50 rabbits were divided into 3 groups; the first group of 9 rabbits were used to determine theavailable dosage of epinephrine as preliminary study, the second group of 18 rabbits were used to evaluate theradiation injury as radiation group, which were received a single dose of 2,000 rads of radiation on unilateralkidney using 60 Co teletherapy unit, and the third group of 23 rabbits were used to assess the radioprotective effedct of epinephrine as radiation -with -epinephrine group, which were received same dose of radiation on unilateral kidney during infusion of 1.0 ug/min of epinephrine for 18 minutes. For each group, intravenouspyelography, urinalysis, gross observation, microangiography and microscopic examination were undertaken to findthe changes as a function fo time following 1,2,3,4,8, and 12 weeks after irradiation. The resuls obtained are summarized as follows; 1. There is no significant difference between the radiation and radiation-with-epinephrinegroup by intravenous pyelography and urinalysis. 2. The gross morphologic changes had little significant role toassess the radioprotective effect of epinephrine. 3. In microangiographic observation, the degree of radiationinjury in the radiation-with-epinephrine group was considerably milder than in the radiation group whic wasrevealed significant findings of poor filling of glomeruli and increased number of arteriolae rectae verae. 4. In microscopic examination, the degree of radiation injury in the radiation-with-epinephrine group was considerably milder than in the radiation group which was revealed significant findings of interstitial fibrosis and tubularde generation. 5. In conclusion, considerable radioprotective effect of epinephrine on the rabbit kidney, which was selectively infused to renal artery during irradiation, in the rate of 1.0 ug/min was observed.