There were 2 groups of 9 and 11 men, from 38 to 57 years old, in a large mental hospital, mostly with chronic schizophrenia but without evidence of physical disorder and with serum cholesterol initially between 200 and 300 mg%. For each group there were 18 periods of 4 weeks. Diets were devised to maintain bodyweight and keep percentage of total energy from fat and protein about the same for all the men in any one period; cholesterol intake was also kept constant during any one period, though in some periods it was increased or decreased by inclusion or removal of egg yolk. Protein provided 15 to 16%, fat either 22 or 37 to 40% of total energy. A 7-day menu cycle was used throughout. Test diets consisted of a basal diet low in fat, to which were added different fats or mixtures of fats differing in degree of unsaturation. The control diet was designed to resemble an ordinary United States diet and supplied 331 mg cholesterol daily.

Blood was taken from the ear after 2, 31/2 and 4 weeks of each diet, for estimation of total serum cholesterol, β lipoprotien cholesterol total fatty acids and lipid P; total serum triglyceride was calculated on assumption that 70% of the cholesterol was esterified. Values at 31/2 and 4 weeks were averaged. Changes in serum cholesterol are tabulated with percentage of energy supplied by different types of fatty acids. Changes in β-lipoprotein cholesterol ran parallel with those in total cholesterol, those in total triglyceride and phospholipid were in the same direction but less consistent. The data were analysed by computer, with type of fatty acid expressed both as percentage of total energy and as percentage of total fat.