It has been widely supposed that human mortality from all causes increases with age nearly exponentially (at a constant rate) through adult ages except for very old ages, and that this exponential increase also holds fairly well for most major causes of death (CODs). However, the present analysis of death registration data for Japan, 1951-1990, reveals that the rate of age-related relative increase in mortality (the life table aging rate) changes with age significantly and systematically for many CODs. Above age 75, the mortality increase decelerates for most CODs; under age 75, it remains at a relatively stable pace for ischemic heart disease, decelerates for most major cancers, and accelerates for diseases related to a declining ability to maintain homeostasis (pneumonia, bronchitis, influenza, gastroenteritis, and heart failure). These results seem to suggest that significantly different types of senescent processes may underlie atherogenesis, oncogenesis, and immunosenescence.