Many chemical substances have been shown to influence renal function (Commandeur and Vermeulen, 1990). The production of mild and reversible changes is pharmacologically important in the development of diuretics and renin-angiotensin inhibitors; in contrast, irreversible changes may occur following administration of some drugs and chemicals. There are several reasons for the susceptibility of the kidneys to injury. First, renal blood flow is approximately 25% of cardiac output and delivers large quantities of blood to the kidneys. especially the cortex. Second, the kidneys have the ability to concentrate the fluid passing through the tubules such that the concentrations of certain drugs and chemicals may increase 100-1000-fold at certain regions, e.g. proximal tubule. Transport processes for cationic and anionic molecules located in the proximal tubule may be blocked by, or used by, chemicals to gain entry into the renal epithelial cells. Third, the presence in the proximal tubules of mixed function oxidase have the potential to transform harmless substances into more reactive metabolites. renders this of the tubule vulnerable to injury.