The study was undertaken to evaluate the protective effect of epinephrine on renal radiation injury. For the experiment, 50 rabbits were divided into 3 group : the first group of 9 rabbits were used to determine the available dosage of epiniphrine as preliminary study, the second group of 18 rabbits were used to evaluate the radiation group , which were received a single dose of 2,000 rads of radiation on unilateral kidney using 60Co teletherapy unit, and the third group of 23 rabbits were used to assess the radiopretective effect of epiniphrine as radiation with-epinephrine group, which were received same dose of radiation on umilateral kidney during infusion of 1.0ug/min o fepinephrine for 18 minutes. For each group, intravenous pyelography, urinalysis, gross observation, microangiography and microscopic examinantion were undertaken to find the changes as a function of time followng 1, 2, 3, 4, 8 and 12 weeks after irradiation . The results obtained are sumarized as follows 1. There is no significant difference between the radiation and radiation-wit-epinephrine group by intravenous pyelography and urinalysis. 2. The gross morphologic changes had little significant role to assess radioprotective effect of epinephrine. 3. In microangiogrpahic observation, 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 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 consideralbly milder than in the radiation group which was revealed significant findings of interstitial fibrosis and tubular degeneration. 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 1.0ug/m in was observed.