The water soluble benzodiazepine midazolam was compared with diazepam, in doses of 0.07 mg kg-1 and 0.15 mg kg-1 respectively, administered i.v. to 100 patients undergoing gastroscopy. The degree of sedation, ease of endoscopy and recovery were comparable in the two groups. The effects of both drugs on arterial pressure were similar. Compared with diazepam, midazolam had a faster onset of effect, caused virtually no pain on injection, and provided a greater degree of amnesia.