The studies reviewed here reflect only a modest and conceptually limited beginning in gerontological pharmacology. Germane to the future course of research is whether prolongation of either mean or maximum life-span brings about a true deceleration of the overall aging process or only in certain biological functions. Prolongevity with out efficacy, that is without the addition of useful years, is merely an academic exercise. Hence, we suggest that agents which prolong life-span should also be tested in the laboratory for their ability to modify those functional parameters which are known to change significantly with age. To list a few, these might include measuring rates of de novo protein (enzyme) synthesis, properties of collagen, and antigen-antibody response. Furthermore, we believe that a scientific attack on specific age-associated decrements in mental and physical function could serve an immensely useful and practical purpose.