An experimental study on the vascular alternations of the kidney following biopsy procedure was carried out in 47 kidneys from 28 rabbits to clarify their nature and frequency by renal arteriography and microangiography together with his topathologic investigation. Renal arteriography and microangiography were performed immediately 2 days , 1 week, and 2 weeks after percutaneous biopsy and the finding were correlated with histological nature. The results are summerized as follows : 1. Important biopsy injuries verified by renal arteriography and mocroangiography were arterial spasm, perfusion defect, arteriovenous fistula injury to vasa rectae and renal tubules, intrarenal and extrarenal extravasation of contrast media, and arterial obstruction , in order of frequency. 2. Arterial spasm observed in majority of the cases were relived during the period of 2 weeks. 3. Detectability of perfusion defect was57 % by angiography and microangiography, respectively, and this perfusio de ect seemed to be mostly caused by renal infarction due to vascular injury, such as arteriovenous fistula, arterial obstruction and other vascular injuries. 4. Arterivenous fistula was detected in 28 % by angiography and 50% by microangiography, Many of the arteriovenous fistulae appeared to be closed spontaneously within a week. Above findings suggest that renal biopsy precedure results in various degree of vascular injuries with their sequential modification, and that microangio grahy is assumed the most effective approach in analysis of biopsyinjuries such as small arteriovenous fistular, perfusion defect, injury to vasa recta and renal tubules, overcoming the limitation of traditional angiography.