Intramuscular midazolam frequently results in excessive sedation in elderly patients. The effects of preanesthetic medication with intramuscular midazolam were examined in 100 elderly patients, aged 60-86 yr, given 1, 2, or 3 mg midazolam or placebo using a randomized, double-blind study design. Level of sedation and anxiety were assessed every 15 min for 1 h. Picture cards were presented at the same times in order to assess recall of these cards 24 h later. All three doses of midazolam produced rapid onset of sedation, anxiolysis, and anterograde amnesia. These effects decreased in intensity by 60 min after drug injection. The intensity and extent of these effects were comparable with those reported with higher doses in younger patients, although with the 1-mg midazolam dose the effects were shorter-lived, and a difference from placebo was not consistently seen. Three patients (3%), all older than 70 yr, became unresponsive to vocal and tactile stimuli. This level of drowsiness was unrelated to body weight, age, or ASA physical status. We conclude that in adults between 60-69 yr old, midazolam 2 or 3 mg intramuscularly can be effective as preanesthetic medication without causing excessive drowsiness. However, intramuscular midazolam should be used cautiously, under continuous observation, in patients aged 70 yr and older because excessive drowsiness may occur.