Aging is one of the most fundamental biological processes. It results in a decline in physiological function and an increased risk for pernicious diseases such as cancer. Oxidative stress has been proposed as a major cause of aging, but experimental tests of this hypothesis have been discouraging. Calorie restriction (CR) prevents age-related decline, but there are still gaps in our knowledge of the exact mechanisms underlying this feat. Finally, a tenuous balance exists between aging and cancer, calling for a search for interventions that prevent both aging and cancer. Recent work on the mammalian sirtuin SIRT3 has shed light on these long-standing issues and suggested new approaches to ameliorate the ravages of aging.