The phospholipids, plasmalogens, cholesterol, and total polyunsaturated fatty acids of 5 pulmonary carcinomas of various types, of a benign clear cell tumor, and of tissues from 2 normal lungs were determined. The phos-pholipid content of 3 of the carcinomas was similar to that of the normal lung; in 2 carcinomas and in the clear cell tumor it was considerably higher. The plasmalogens were at a low level. The major part of cholesterol was unesterified. None of these lipids correlated to cellularity or histologic pattern. All of the polyunsaturated fatty acids except the trienoic acids were present in substantially larger amounts than in lung or any other tissue except brain and testes, the tetraenes and dienes being particularly abundant. The carbohydrate content of the carcinomas was minimal, that of the clear cell tumor very high.