Little is known about the effects of obesity late in life. Using data from the Longitudinal Study of Aging and the Assets and Health Dynamics of the Oldest Old Survey, this study finds an increased prevalence of obesity, over time, among those 70 and older. Obesity is related most strongly to limitations in activities of daily living (ADLs) for women and to activities related to mobility. One ADL, eating, has a negative association to obesity. Obesity is associated with an increased prevalence of arthritis, diabetes, and hypertension. These results are cross-sectional and are based on self-reports of height and weight; they must be interpreted cautiously.