Phospholipid composition was studied in membranes of various tissues as well as of mitochondria and erythrocytes of rats with alcohol intoxication. A new phospholipid--phosphatidyl ethanol, which was absent in tissues of control animals, was detected in liver, heart, kidney, small intestine tissues as well as in erythrocytes and liver mitochondria of rats consuming ethanol independently on the alcohol administration procedure used. Studies of rat liver mitochondria and mitochondrial "ghosts" showed that formation of phosphatidyl ethanol and phosphatidic acid was catalyzed by membranal endogenous phospholipase D. Phosphatidyl ethanol appears to be of importance in membranotropic effect of ethanol--one of main factors participating in alcohol pathology development. This phospholipid was found also in erythrocytes and blood of patients with chronic alcoholism, which were subjected to alcohol provocation before examination. In erythrocytes of the other group of patients with chronic alcoholism, not provocated with alcohol, the phosphatidyl ethanol fraction was not found but content of phosphatidyl ethanolamine was distinctly increased. In patients with delirium tremens phosphatidyl ethanol was not observed, content of phosphatidyl ethanolamine was not increased, while amount of phosphatidic acid was considerably elevated.