A single experiment, conducted over a period of two years, showed that the life span of a given number of flour beetles (Tribolium confusum) may be extended several percent by exposure to gamma-radiation, either as a single exposure of about 3000 r or chronic daily doses of about 100 r. The cumulative effect of chronic irradiations is not equivalent to that of the same total. Twenty percent of the animals receiving 100-r daily lived more than 450 days. In that time they received 45,000 r, more than twice the amount that would have produced complete annihilation in a single irradiation. Organisms surviving a single large dose of gamma-rays have a survival rate superior to that of non-irradiated controls.