AORTOGRAPHY is a remarkably innocuous procedure considering that at least 30 gm of an organic salt containing 50% to 70% iodine is introduced into the circulation within a period of two to three seconds. However, complications have been reported and the kidney appears to be the most vulnerable organ.1Extensive investigations have been carried out to determine the mechanisms responsible for the toxicity of radiopaque materials. Previous work2-4from this laboratory has emphasized the role of red cell crenation and aggregation with a resulting increase in blood viscosity. These changes may lead to thromboembolism and ischemia. The purpose of the present study was to determine whether renal damage arising from angiographic media represents a direct toxic effect on the parenchyma5or is, as has been demonstrated for concentrated saline,6a secondary phenomenon related to changes induced in the renal circulation. Methods The experimental preparation used in