During the past 15 years, our aging colony of rhesus monkeys, consisting of animals from 20 to 37 years of age, had an annual average population of 88.2 live monkeys and, of this population, an annual average of 13.9 monkeys died spontaneously or were terminated due to severe illness. From 1980 to 1994, a total of 175 autopsies of rhesus macaques, from 20 to 37 years of age, were performed. By cumulative autopsy data, the incidence of age-related pathology in various organs was surveyed. Major geriatric diseases such as coronary sclerosis, emphysema, degenerative joint disorders, cancer, and cerebral amyloid plaque began to develop in 10 to 40% of macaques after 20 years and the incidence significantly increased after 26 years of age. Approximately 12% of aged macaques from 20 to 30 years of age died annually due to such geriatric diseases with severe complications. The average survival rate indicated that half the population at 20 years of age died by 25 years and 73% died by 30 years of age. Less than 10% of macaques survived over 30 years. Using these aged macaques as well as other juvenile to adult monkeys in our Center, clinical opththalmological and reproductive endocrinological studies, and magnetic resonance imaging (MRI) of the brain were conducted to define bioaging markers of captive rhesus monkeys. Cataracts began to develop in 20% of rhesus monkeys at 20 to 22 years of age and the rate significantly increased after 26 years of age. Menopause occurred at 26 to 27 years of age. Multiple cerebral infarctions and iron deposits in the globus pallidus and substantia nigra were detected by MRI in the aged brains. These geriatric disorders in captive aged macaques appear to be natural aging outcomes, since the simple lifestyle of these captive animals offers minimal exposure to environmental factors. Our data will offer useful paradigms for preventive or experimental studies on age-related diseases.