In order to clarify the early mechanism of action of the tissue necrosis induced by intraarterially infused absolute ethanol, abdominal aortography and histopathologic examination after absolute ethanol infusion into aorta at fast(0.4$mell$/sec) and slow speed(0.04$mell$/sec) were performed on 22 rats(2 controls, 7 in fast infusion group, 7 in slow infusion group, 3 in fast and 3 in slow infusion groups during aorta compression, respectively). Histopathologic features under the light and scanning electron microscope were correlated with the angiographic findings within 30 minutes after ethanol infusion. The results are as follows ; 1. In fast infusion group, histopathologic examination of the kidney showed severe glomerular and tubular damage. Extensive damage on endothelial and medial layer was noted in arteries, and fresh thrombi originated from the damaged arterial wall were seen. 2. Angiographic findings in the fast infusion group were luminal irregularity and early obstruction of large arteries. And circulation time was prolonged. 3. In slow infusion group, histopathologic examination of the kidney showed focal area of severe glomerular and tubular damage on relatively normal background. endothelial and muscular damage was noted in arteries, but the degree of the damage was less severe than that of the fast infusion group. 4. Angiographic findings in the slow infusion group were focal perfusion defect of the kidney, delayed circulation time, and mild luminal irregularity, but obstruction of the major arteries was not seen. 5. Aorta compression group had only minima angiographic and histopathologic alteration compared with uncompressed fast infusion group, although hemorrhage and cast of desquamated cells in renal pelvis noted in compression group suggested the possibility of severe tubular damage and venous thrombosis. 6. In conclusion, there was difference in angiographic and histopathologic features between fast and slow infusion group. It is suggested that thrombus formation from the damaged vessel walls is the initial process leading to the obstruction of the arteries and necrosis of the target organ as well as the damage on the endothelium and perivascular tissue. The amount of the fresh platelet thrombi originated form the damaged endothelial surface and the mechanical occlusion of the arteries with the secondary emboli are the factors which determine the initial angiographic features of the ethanol infused organ. secondary emboli formed in slow infusion group might obstruct the proximal arteries so that protect the cells in distal area from the toxic effect of absolute ethanol. Therefore, the fast infusion of the ethanol is preferred to the slow one for the condition which requires complete ablation of the distal organ. 7. effect of absolute ethanol in aorta compression group needs further investigation.