The phenomenon of longevity hormesis is reviewed. The life-prolonging effects of longevity hormesis are compared and contrasted with those resulting from depressed food intake. The use of age-specific mortality rate analysis as a tool to characterize the separate and distinct effects of longevity hormesis, cumulative toxicity and depressed food intake on the survival of laboratory animals is illustrated. Finally, model systems through which the mechanism(s) of longevity hormesis may be elucidated are discussed.