Renal arterial embolization was induced experimentally in rabbits using autologous blood clot, Geelfoam. barium sulfate, lvalon (Polyvinyl alcohol) and ethanol. Microvascular changes were studied angiographically, microangiographically and histopathologically. The results were as follows : 1. The microangiographic findings of renal artery embolization were arterial occlusion, irregular arrangement, spiralling, dilatation, narrowing and collateral vessel formation. 2. Recanalization of embolized vessels were noted after injection of autologous blood clot and Gelforam only. 3. Collateral vessel formations were demonstrated in entire cases of renal arterial embolization (36/37) 4. After injection of lvalon, recanalization of embolized vessel was not demonstrated but collateral vessel formations were demonstrated microangiographically in all cases. 5. Afger injection of ethanol, collateral vessels were poorly developed microangiographically than other groups. 6. Embolic effect of ethanol was noted I central vessel but as well as in peripheral vessel. it was considered that ethanol is the most effective agent for permanent renal arterial occlusion.