Risks associated with drug therapy are more prevalent with advancing age. In drug evaluation it is imperative to identify risk groups. Six strategies are discussed to identify risk groups: (a) from physico-chemical, preclinical drug data, and expected physiologic changes; (b) from animal and human phase I PK data and expected physiologic changes; (c) from epidemiologic data and expected physiological changes; (d) from animal/human toxicokinetic data and expected physiologic changes; (e) from retrospective patient monitoring; (f) from population kinetics using NONMEM; and (g) from pharmacokinetic screen approach.