Geriatric patients often have several diseases so that in the acute phase the doctor has to treat with many drugs simultaneously. Elderly persons are more vulnerable to drug effects, both therapeutic and adverse. Physiological and pathological changes with aging influence geriatric drug therapy. Pharmacokinetic differences are generally consistent with age differences in renal and liver function, body composition, tissue perfusions, protein and cellular binding. The present paper gives some examples (glycosides, anticoagulants) of drug therapy and adverse reactions.