Elderly patients pose special pharmacological problems. The combination of failing health, an aging body, and multiple drug prescriptions can alter drug effects clinicians would expect to occur in younger patients. Clinicians may also encounter problems of noncompliance or capricious compliance when treating older patients. They should be aware that elderly patients are more susceptible to psychotropic drug toxicity, severe extrapyramidal side-effects from neuroleptics, and anticholinergic side-effects from tricyclic antidepressants. Clinicians should make a complete medical evaluation and determine all of the medications an older patient is taking before they prescribe a psychotropic drug.