To estimate and compare the awakening period following 4 different anaesthetic techniques (enflurane and halothane and two intraveinous anaesthetic substances: propanidide and althesin), the authors examined 120 outpatients who had undergone maxillo-facial surgery distributed over 4 sample groups of 30 each. A statistical analysis of the responses to psycho-dianostic tests has not enabled the authors to decide which anaesthetic ambulatory technique is preferable.