Ethionine induces necrosis of the distal portion of the proximal convolutions in the rat kidney. On a normal diet renal involvement is more frequent and more extensive in male animals. Protein depletion increases very markedly the susceptibility of the kidney to the nephrotoxic action of ethionine in male and female rats. Methionine inhibits the renal toxicity of ethionine; glycine and alanine are without effect.