Thirty-one patients undergoing neuro-radiological investigations were anesthetized by methohexital-fentanyl association. Induction of anesthesia was performed by I. V. bolus of these two agents. Anesthesia was maintained by a constant rate perfusion of methohexital and fentanyl, prepared according to body weight. Posology can be reduced hourly by modifying the perfusion rate. First hour: methohexital 2 mg/kg/hour fentanyl 5 microgram/kg/hour; second hour: methohexital 0.4 mg/kg/hour, fentanyl 2 microgram/kg/hour; third hour: methohexital 0,4 mg/kg/hour, fentanyl 1 microgram/kg/hour. If necessary this dosage was modified according to isolate reactions and thus total real consumption was 25 to 30 p. cent higher to estimated theoretical requirements. This protocol of anesthesia with controlled ventilation was well cardiocirculatory tolerated and adapted to these radiological investigations.