We investigated whether positioning patients undergoing general anaesthesia for cholecystectomy in a 20 degrees head-up position, as opposed to supine, improved the efficacy of 3 min of standard pre-oxygenation via a circle breathing system. Following pre-oxygenation, patients received a standard induction of anaesthesia and the apnoea time (from administration of rocuronium to the arterial oxygen saturation to fall to 95%) was recorded. Mean (95% CI) apnoea time was 386 (343-429) s in the 20 degrees head-up position (n = 17) vs 283 (243-322) s in the supine position (n = 18; p = 0.002). Pre-oxygenation is significantly more efficacious and by inference more efficient in the 20 degrees head-up position than in the supine position.