Midazolam, a new water-soluble benzodiazepine, was given intravenously in 5 and 10 mg doses to nine volunteers and plasma levels estimated at intervals for 24 hours. Recovery was also studied. the drug was easy and painless to inject and venous thrombosis was not found in this series. While there was a great individual variation in response to the drug this was not related to the weight of the subjects. Plasma levels declined rapidy and there was no 'second peak' effect. The half-life was between 60 and 90 min. Recovery was much more rapid than after comparable doses of diazepam.