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 aortaat fast(0.4ml/sec) and slow speed(0.04ml/sec) were performed on 22 rats(2 controls, 7 in fast infusion group, 7 inslow 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 rsults are as follows: 1. In fast infusion group, histopathologic examination of the kidney showed severe glomerular and tubular damage. Extensive damage onendothelial and medial layer was noted in arteries, and fresh thrombi originated from the damaged arterial wallwere 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 facal 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 infusiongroup. 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. Aortacompression group had only minimal 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 differencein angiographic and histopathologic features between fast and slow infusion group. It is suggested that thrombusformation from the damaged vessel wall is the initial process leading to the obstruction of the arteries andnecrosis of the target organ as well as the dmage on the endothelium and perivascular tissue. The amount of thefresh platelet thrombi originated from the damaged endothelial surface and the mechanical occlusion of thearteries with the secondary emboli are the factors which determine the initial angiographic feature of the ethanolinfused organ. Secondary emboli formed in slow infusion group might obstruct the proximal arteries so that protectthe cells in distal area from the toxic effect of absolute ethanol. Therefore, the fast infusion of the ethanol ispreferred to the slow one for the condition which requires completer ablation of the distal organ, 7. Effect ofabsolute ethanol in aorta compression group needs further investigation.