The elderly population experiences a normal, age-related decline of physiological function in all major organ systems. The age-related changes in lung structure include decreases in chest wall compliance, respiratory muscle strength and elastic recoil, contributing to decreased lung function which increases susceptibility to infection. The age-related changes in cardiovascular structure and function increases the risk of cardiovascular disease. The aging process in the kidney leads to several clinical conditions in the elderly such as impaired drug metabolism and kinetics, loss of homeostasis, and electrolyte abnormalities. With aging, the decrease in gastrointestinal (GI) function in the mouth, esophagus, stomach, small and large intestine, and liver may affect appetite, motility, enzyme and hormone secretion, nutrient digestion and absorption, and gastrointestinal immunity. These changes in GI function may play a significant role in malnutrition and an increased risk of cachexia. Aging leads to inevitable deterioration in cellular and physiological function, which result in impaired homeostasis, decreased ability to adapt to stress, increased vulnerability to disease, and increased age-related mortality. Optimal health care management requires a deep understanding of the normal physiological changes associated with aging, and is necessary to provide insight into the mechanisms of multiple organ impairment and disease in the elderly.