Male wistar rats were housed in laboratory cages or activity-wheel cages at eight 10.5 or 18 months of age. Part of each cage group continued to be fed ad libitum, whereas the remaining animals were fed every other day. Compared with the ad libitum condition, intermittent feeding decreased body weight and increased lifespan at both ages in both caging conditions. Compared with the caged condition, voluntary exercise in activity wheels reduced body weight only in the 10.5-month-old group fed ad libitum but produced no effect on survival of either age group. The results suggest that intermittent feeding can enhance survival in mature rats even beyond ages at which body weight growth usually ceases, whereas voluntary exercise appears to have an early threshold beyond which increases in longevity are not observed.