Older persons have altered responses to drugs because of physiologic and anatomic changes which influence drug absorption, tissue localization, metabolism, receptor sites, homeostatic adjustments, and excretion. Deteriorating mental and physical faculties produce other untoward, bizarre, or exaggerated effect. This paper reviews problems in the use of endocrines, antihypertensives, cardiac glycosides, analgesics, psychoactive drugs, antibiotics, antiparkinsonians, iron, anticoagulants, gastrointestinal agents, and ophthalmics and some factors involved in allergenics and drug-induced jaundice. The elderly also often have problems involving the proper use of drugs, obtaining drugs, or in the improper use of non-prescription drugs. Suggestions are made for the physician and pharmacist to keep these problems to a minimum.