We describe the physiology of aging and its effect on elderly, critically ill, surgical patients. Postoperative age-specific complications and their management will be reviewed. The number of elderly persons, defined as those >65 yrs of age, is the fastest growing segment of the U.S. population. As a result, the frequency of surgery, both elective and emergent, performed on elderly patients will increase. Aging is associated with a decrease in the physiologic reserve; thus, many elderly persons are unable to compensate for the increased metabolic demands that accompany acute illness or injury. This inability to compensate leads to increased rates of postoperative complications and death. Aggressive, goal-directed management in the surgical intensive care unit is beneficial for the geriatric patient. The management of the elderly, surgical, critical care patient is extremely challenging. Understanding age-related physiologic changes will help guide treatment to maximize outcome and prevent complications.