To intubate under ideal conditions, i.e. with the vocal cords abducted and no motor response to the insertion of the endotracheal tube, the anaesthetist has two alternatives : to use muscle relaxants or to anaesthetize the patient deeply. Apart from cases where muscle relaxants are contra-indicated or required by the type of procedure: Intubation using muscle relaxants means: - maintaining the option of varying the depth of anaesthesia, while keeping optimal conditions for intubation; - reducing the risk of airways trauma. Intubation without muscle relaxants means: - avoiding the risk of allergic complications; - producing deep anaesthesia and controlling any resulting haemodynamic effects. The recommended induction agent is propofol, given as a bolus injection at a dose equal to or greater than 2.5 mg . kg-1 in adults and 3.5 mg . kg-1 in children. Alfentanil is the opioid of choice, the dose being between 30 and 40 mug . kg-1. Lidocaine, injected as premediation at a dose of 1.5 mg . kg-1 potentiates the effect of alfentanil. The order of injection of the induction agents is important, as it determines the exact moment for laryngoscopy and intubation.