Drug-induced cognitive impairment is a common cause of delirium and is frequently a confounding factor in dementia. Predisposing conditions for delirium include age, brain disease and addiction to alcohol and/or drugs. The elderly are at particular risk because of multiple diseases, multiple drug use and alterations of drug metabolism associated with age. Sedatives such as benzodiazepines have a particularly high risk of cognitive impairment. Centrally acting sympathetic antihypertensive agents, sedating antipsychotic drugs, opioids, digitalis, anti-Parkinsonian drugs, antidepressants and corticosteroids are also associated with greater risk relative to other classes of medications. Cognitive impairment due to medication may be reduced by recognition of the problem. The risk of drug-induced impairment may be minimised by strategies which optimise overall health, avoidance of unnecessary medications, and selection of medications least likely to cause delirium.