Adult mongrel dogs were used to evaluate and compare the use of ethanol and ethanol-Ethiodol for transcatheter renal arterial embolization. Each agent was administered into a main renal artery in five dogs and evaluated with regard to ease of use, radiopacity, arterial occlusion, parenchymal damage, and toxicity. Both agents were easy to inject, and no complications were encountered in any of the animals. Ethiodol added the ability to fluoroscopically monitor the infusate for reflux and distribution, yielded a more homogeneous distribution of the ethanol within the renal vasculature, and increased the embolic effects of the ethanol. Adding Ethiodol to ethanol should decrease the latter's complications since administration can be monitored fluoroscopically and a smaller volume of ethanol could perhaps be used to achieve the desired result. Additional research is needed to determine the safety of administering larger volumes of Ethiodol into the renal artery.