The disappearance of native labeled plasma phospholipids (nPLP32) was abruptly halted in the plasma of normal mongrel dogs shortly after givingdl‐ethionine by intraperitoneal injection. In other dogs, chronic feeding of ethionine over a period of three days prior to these measurements prolonged the turnover time of plasma phospholipids. This impairment in the turnover of plasma PL brought about by ethionine administration occurs regardless of sex differences in lipid metabolism or other physiological differences relating to the nutritional status of the animal. The amount of nPLP32 found in the liver at the end of the turnover experiments was also measured. These data suggest that phospholipid transport from plasma to liver is not impaired by ethionine. The possible significance of an ethionine‐induced choline deficiency which impairs transport of triglycerides and phospholipids from the liver to plasma is considered in regard to the role of phospholipids in the triglyceride cycle.