Standard venographies were pcrformed to evaluate the endothelial damage by the contrast medium. After different time intervals, the local veins were prepared for transmission and scanning electron microscopy (TEM and SEM) investigation. The veins were in a dilated state after the angiographies, which lasted for about two days. The endothelial damage was most severe 1 day after the venography. Besides the lesions of extensive endothelial tissurs, dcsquamations, and the exposure of subendothelial tissues, microthrombi somethimes were found. Healing occurred within 3 days. The results this study has also verifieed that it was more valuable to study venogqaphic effects on veins with TEM and SEM.