This study was designed to observe the effects of both control and atherogenic diets on the cholesterol and triglyceride (TG) in serum and liver of adult rats fed diets supplying two levels of dietary fat and two different sources of dietary protein in early life. For the first experimental period, the rats were assigned into the four diet groups: High fat, casein (HC); High fat, gluten (HG); Low fat, casein (LC): Low fat, gluten (LG). Each group was subdivided into control and atherogenic groups for the second experimental period. Cholesterol and TG were determined in serum and liver after 7 hr fasting. The body weight gain was greater in the rats of the casein groups than those of the gluten groups tut not influenced by the level of the dietary fat. The difference in body weight from the quality of dietary protein in the first period was not disappeared even after the second period. After the first period, higher serum cholesterol was observed in the rats fed either casein or high fat diets. With the second experimental diet, rats fed atherogenic diet showed higher serum cholesterol concentration but lower serum TG levels compared to those fed control diet, regardless the diets fed in the first period. Serum cholesterol level of the rats of both groups which had been fed high fat diets in early life was increased compared to those of the low fat diet groups. This effect was more pronounced with the atherogenic diet groups than control groups. However, no differences were found in serum cholesterol levels resulted from the different types of dietary protein fed in the first period. Serum TG concentration was not influenced by the quality of protein and level of fat in the diet but seemed to be mere affected by the amount of carbohyrates in the diet. Liver cholesterol per unit weight was greater in the gluten diet groups than in the casein groups but total cholesterol was higher in casein fed rats. There were no differences in liver TG among the groups.