Intravenous midazolam was tried as a hypnotic agent for induction of anesthesia in 63 surgical patients. Three dosages were used: 0.2, 0.3 and 0.4 mg/kg body weight. Indices of induction, changes of vital parameters, incidence of apnea and side effects and the duration of the drug effect on central nervous system functions were evaluated. No significant differences were observed between the effects of the different doses of midazolam on the cardiac and respiratory parameters. The drug provided a satisfactory degree of sleep in all patients of maximal intensity at three minutes but anesthetic induction was not achieved in several patients of each dose group (overall failure rate 11%). A short-lasting apnea was seen in 13% of the patients and seemed not related to the administered dose of midazolam. The awareness of the surroundings was satisfactorily obtunded by the anti-recall effect of the drug. The sedative effects of midazolam on central nervous system functions lasted fairly long. Indeed, mental arousal, sensory functions and muscle tone still had not returned to preinjection values 20 min after midazolam administration. A reliable relationship between dose of midazolam and intensity of cerebral depressive effect was not evident.