The anesthesiologist is a doctor who intervenes before, during and after any surgical operation requiring general or regional anesthesia. During a preoperative consultation, he assesses the general condition of the patient, chooses the most suitable anesthesia technique appropriate and reassures the patient. His psychological role at this stage is far from negligible. In “operating room”, in case of general anesthesia, the anesthesiologist applies a mask diffusing an instantaneous effect gas or injects an intravenous analgesic. intervention, and in close collaboration with the surgeon, he uses ultra-sophisticated equipment (electrodes, monitor, defibrillator, blood oxygen measuring device, neurostimulator, etc.) to monitor the patient’s condition, and intervene if necessary. Throughout this so-called safety phase of the operation, the anesthesiologist is himself assisted by a nurse anesthetist.After the operation, the anesthesiologist controls the resuscitation of the operated on in the recovery room, then provides postoperative follow-up. Besides scheduled interventions or operations, the profession is also practiced in an emergency (accidents, poisonings, critical situations, etc.). In this case, the anesthetist must intervene with cold blood and speed to understand the origin of the problem or the problems and to put in place the appropriate resuscitation techniques.