Renal artery embolization was induced experimentally in rabbits and microvascular changes were studied angiographically, mocroangiographically and histopathologically. The results were as follows : 1. The main microangiograhic findings of renal artery embolization were arterial occlusion and collateral vessels are characterized by spiralling, dilatation, irregular lumen with abrupt caliber change, disoriented course and increased number. 2. Collarteral vessel formation was demonstrated in all cases of renal artery embolization by microangiography. 3. REcanalization of embolized vessels was better visualized by renal angiography than microangiograhy. It was considered that microangiography is a valuable method for the observation of microvascular changes in renal artery embolization and other renla diseases.