Cholinergic blockade by scopolamine, a central muscarinic receptor antagonist, may produce transient memory impairment in healthy subjects, and it has been used as a neurochemical model of cognitive degeneration in aged individuals. To observe the muscarinic modulation of memory and cortical auditory processing, nine cognitively intact elderly subjects (59–80 years) were studied using neuropsychological tests and 122-channel magnetoencephalography (MEG) after an administration of scopolamine hydrobromide (0.3 mg, iv) or glycopyrrolate (0.2 mg, iv), a peripheral muscarinic antagonist. A double-blind randomized crossover design was used in two sessions separated by at least 1 week. Scopolamine, but not glycopyrrolate, produced a transient impairment of verbal memory performance in the elderly subjects. MEG indicated that the auditory-evoked 40-Hz magnetic response was significantly larger after scopolamine than after glycopyrrolate administration. Furthermore, reanalysis of our earlier results in younger subjects (20–31 years), basically supporting the present MEG findings, tentatively suggests that the scopolamine effects on the 40-Hz response may be slightly pronounced with aging. In sum, the transient magnetic 40-Hz auditory response may be useful in studies on brain cholinergic deficits in elderly subjects.