Angiographers responding to a questionnaire disagreed on the agent of choice for selective renal arteriography. Opinion differed regarding the advantages of sodium versus meglumine salts, diatrizoate versus iothalamate, and 50-60% concentration agents versus those in the 70-76% range. Although an increasing number of angiographers are using more concentrated agents for renal arteriography, there is little information available to indicate their safety for this purpose. Dog experiments were done to see whether Renografin 76% (R-76), at a reasonable dose, caused more severe changes than the lower concentration agents. The studies failed to demonstrate significant differences between R-76 and the less concentrated agents indicating that R-76 can be used for selective renal arteriography if the additional iodine is deemed necessary. Factors affecting nephrotoxicity of contrast media in patients with normal and abnormal kidneys are discussed.