Long-term feeding of adenine to rats produced metabolic abnormalities resembling chronic renal failure in humans. Among the disturbances produced were azotemia, accumulation of uremic toxins, metabolic imbalances of amino acids and electrolytes, and hormonal imbalances. The pathological findings in the kidneys of these experimental rats revealed lesions of proximal tubules, of some distal tubules and of glomeruli. Contracted kidneys were found in the rats with severe perturbations. Our results suggest that long-term adenine feeding provides a model which would be useful to study chronic renal failure.