Anticholinergic effects of the 25 drugs most commonly prescribed for the elderly were measured by radioreceptor assay. Fourteen had detectable anticholinergic drug levels; 10 of these had levels that have been associated with impairments in memory and attention in normal elderly subjects. These data indicate that patients taking multiple medications may be at increased risk for side effects from psychotropic drugs, most of which have anticholinergic effects.