The metabolism of cholesterol was studied in baboons, rhesus monkeys, and squirrel monkeys while they were being fed either a low fat, low cholesterol (basal) diet or the basal diet supplemented with saturated fat and cholesterol (atherogenic diet). When the diet was changed from basal to atherogenic, the mean total serum cholesterol concentration increased from 70 to 180 mg/dl in the baboon, from 168 to 283 mg/dl in the squirrel monkey, and from 144 to 608 mg/dl in the rhesus monkey. In animals fed the atherogenic diet, the percentage of dietary cholesterol absorbed was greatest in the rhesus monkey and least in the baboon. The fraction of the total body pool of cholesterol that was derived from the diet was greatest in the squirrel monkey and least in the baboon. The turnover of the body pool of cholesterol was several times faster in the squirrel monkey than in the baboon or the rhesus monkey when either dict was fed. The mean total fecal excretion of endogenous cholesterol and bile acid increased in all species on transition to the atherogenic diet; however, the relative contributions of the neutral and acidic fractions to the increase in total excretion differed among species. The difference in percentage of dietary cholesterol absorbed may, in part, account for the large differences in serum cholesterol during the atherogenic diet period. Comparison with other published results indicates that of these species cholesterol metabolism in the baboon is most like that in the human.