SUMMARYA study of the cardiovascular effects of intravenous chlormethiazole (Heminevrin) was carried out on five volunteers. It showed that induction of light anaesthesia was easy, maintenance easy, and the recovery period short and uneventful. During induction, maintenance and recovery the only cardiovascular disturbance noted was an increase in heart rate; cardiac output was maintained at the pre-induction level. In view of the results obtained in this series and the clinical experience of its use in an assisted ventilation unit, it is suggested that chlormethiazole would be a suitable agent to provide sedation during many of the procedures required in an intensive care unit.