It has been demonstrated repeatedly that the administration of ethionine, a methionine analogue, will produce destruction of pancreatic tissue and liver cells. Destruction of acinar cells of pancreas by the administration of excess methionine similar to that seen after feeding diets supplemented with ethionine was also reported, but the liver was not involved by this amino acid. In an attempt to reproduce the results of these investigators the tissue damages were found to be slight and seen only irregulary in rats receiving ethionine on a complete diet and the result of tissue damages by excess methionine were also controversial. The present studies describe the toxicity of dietary supplemented ethionine and methionine to liver and pancreas in rats fed a low protein diet. Hundred five albino rats weighing around 120 gm were divided into three groups as follows; 1) Control group: A low protein diet containing 8% casein was fed throughout the experimental period. 2) Methionine group: A low protein diet (7% casein) supplemented with 1% methionine was used. 3) Ethionine group: A similar diet as methionine group except the supplementation of 1% ethionine instead of methionine was used. Five animals per wee from each group were killed for 6 weeks. The liver and pancreas were fixed in 10% formalin and histologic sections were prepared and stained with hematoxylin eosin. Serum amylase was expressed as much of glucose liberated from a starch substrate. The glucose was determined by the method of Nelson (1944). Serum glutamic pyruvic transaminase (SGPT) and glutamic oxaloacetic transaminase (SGOT) were determined by the technique described in Sigma Bulletin.