The phospholipids, total cholesterol, free cholesterol and cholesterol esters of the sera of cancer and non-cancer patients vary within wide limits, associated with food intake, medicine, age, sex, irradiation and season. The average values of the 4 substances in cancer patients are 150.5, 152.2, 76.7 and 75.7 mgm. % and for the non-cancer patients 178.7, 169.3, 77.2 and 92.1 mgm. %. For cancer of the liver and gall bladder the numbers are 426, 261, 184 and 78 mgm. % as compared with 209, 207, 123 and 84 mgm. % for non-cancerous diseases of these organs.