Dietary phosphorus restriction can prevent the progression of renal failure in subtotally nephrectomized rats or in rats with nephrotoxic serum nephritis, independent of protein and caloric intake. Conversely, diets high in phosphorus content result in a more rapid deterioration of renal function. The results are less compelling in indicating that phosphorus restriction can slow the progression of renal failure in the clinical setting. The toxicity of phosphate appears to be related to induction of calcium phosphate precipitation, resulting in tubulointerstitial disease. Most studies of prevention of renal calcification have addressed a single pathway in the development of nephrocalcinosis. These include inhibitors of calcium phosphate precipitation, calcium channel blockers, or an inhibitor of PTH secretion. All of these studies have shown a beneficial effect in preserving renal function. It is possible that a combination of these agents, started early in the course of CRF, may have an additive effect in preventing the progression to ESRD. The discussion of other factors associated with progression of renal failure is beyond the scope of this review. It is obvious that dietary protein restriction, treatment of systemic and intraglomerular hypertension and lipid abnormalities, and prevention of iron overload, all play roles in the preservation of renal function in CRF.