Midazolam (Ro 21-3981; Dormicum ) is a new water-soluble benzodiazepine. Compared with diazepam and flunitrazepam, it has the advantage of a short half-life and good tolerability after intravenous administration. It induces light sleep 1/2 to 2 min after injection, and anterograde amnesia. It has minimal hemodynamic and respiratory effects. We administered midazolam by intravenous injection in a dose of 3-7 mg to 100 patients about to undergo esophago-, gastro-, or duodenoscopy. The patient became quiet and relaxed, falling into a light sleep but remaining capable of following simple instructions. After completion of the endoscopy, the patients were half awake, and listened attentively to the report. They subsequently usually slept for 1-2 h, afterwards remembering nothing of the procedure. Two (at most, 3) hours after injection, the patients were again completely awake and able to go home or back to work. In some cases, concentration was slightly impaired for the rest of the day. Compared with other premedications , midazolam is better suited for use in endoscopy, owing to its rapid onset and short duration of action.