Deposition of lipofuscin autofluorescent granules, is an important phenomenon in the aging process. Cardiac lipofuscin in Japanese monkey (Macaca fuscata) first appears at approximately two years of age. Thereafter, the amount of cardiac lipofuscin increases with increasing age. The first appearance of cardiac lipofuscin shows a good correlation with the maximum life span of animals. Moreover, the rate of lipofuscin accumulation is inversely correlated with life span energy potential (LEP) of animals. From these results, it is suggested that the rate of lipofuscin accumulation depends on the total life span energy expenditure of the tissue.