The current study was undertaken to determine the effect of the dietary cholesterol on the serum cholesterol level in male and female broilers with age. Commercially hatched, a day old broiler chicks of Hisex-Hybro strain were used as experimental animals. Both male and female broilers were divided into 2 groups of 6 birds each on the basis of body weights. Each bird was individually housed in wire cages and was given an experimental diet ad lib for 14 weeks. During the first experimental period of 4 weeks, broilers were fed semipurified diets and in all remaining subsequent periods commercial grain diets were given. Weight gain, feed intake, and levels of total cholesterol, HDL-cholesterol and VLDL+LDL-cholesterol in serum were determined. The results obtained are summarized as follows. 1. There were significant differences in total serum cholesterol concentration between cholesterol-fed groups and controls during cholesterol-loading peridos in both sexes. Feeding cholesterol resulted in higher serum cholesterol both in young and old broilers, and in male and female birds. There were no sex differences in the level of total serum cholesterol throughout all the experimental periods both in cholesterol-fed groups and controls. 2. The rate of increase or decrease in total cholesterol concentration by cholesterol loading or unloading was different between young (0-4 wks of age) and old broilers (7-11 wks of age). Cholesterolemic response of old broilers under cholesterol loading were slower than those of young broilers. In addition, the extent of the rise in total serum cholesterol was greater in old broilers than in young broilers. 3. HDL-cholesterol was not affected by dietary cholesterol. Moreover there were no significant differences in HDL-cholesterol between groups of different ages and sexs. However, the level of VLDL+LDL-cholesterol was markedly increased by dietary cholesterol. In conjunction with the increase in serum cholesterol and unchanged level of HDL-cholesterol with age, it appears that the major component of increased serum cholesterol with age is VLDL+LDL-cholesterol.