This study was carried out to investigate the effect of dietray carbohydrate level on the lipid and Ca metabolism, and on immune response in the process of aging. Spragulcornerue - Dawley male rats of 12 months of age were fed either high carbohydrate or low carbohydrate diet for 9 months. With increasing age from 12 months to 21 months, there was no significant increase in body weight, however, the epididymal fat pat weight and total serum lipid tend to become higher, and the inorganic/organic matterratio in bone tends to become lower. This suggests that body fat accumulation increase and bone mass decrease with age. Rats fed low carbohydrate diet showed the higher epididymal fat pat weight, and the lower Ca content in femur and scapular compared to high carbohydrate diet fed rats. The immune response was also lower in low carbohydrate diet group judged by the lower thymus and spleen index and by the lower response to PHA and ConA stimulation. The results of this study suggests that the dietary level of carbohydrate and fat may play an important role in the process of aging. It could be recommended to practice high carbohydrate -low fat diet for the elderly to reduce the risk of degenerative diseases.