Clinical trials using very low protein supply supplemented with amino acid or keto acid preparations have shown the possibility of slowing the rate of decline of renal function in patients with advanced chronic renal failure together with preservation of nutritional status. The possible mechanisms by which this effect is obtained are reviewed. The potential advantages of keto acids upon amino acids, the optimal composition of the preparations used, and the best time to start treatment in chronic uremics are discussed. Projection of recent data indicate that a prolongation of renal autonomy of about 4 years instead of a spontaneous duration of 15 months until dialysis can be expected using keto acid treatment if started when plasma creatinine reaches 500 mumol/l.