The Laryngeal Mask Airway Supreme (LMAS) is a new, single-use laryngeal mask airway with gastric access. We conducted a randomised controlled study comparing the LMAS with the reusable ProSeal Laryngeal Mask Airway (PLMA) in 70 patients undergoing general anaesthesia with paralysis for gynaecological laparoscopic surgery. Our primary outcome measure was the oropharynegal leak pressure. We also compared the two devices for ease of insertion, adequacy of ventilation and incidence of complications. Both devices had similar rates of successful insertion at the first attempt (LMAS 94% vs PLMA 91%). There was no difference in the time to establish an effective airway (LMAS 25 +/- 22 vs PLMA 24 +/- 9 seconds), although gastric tube insertion was faster for the LMAS (5 +/- 1 vs 7 +/- 3 seconds, P < 0.001). The mean oropharyngeal leak pressure in the LMAS was significantly lower than in the PLMA (27.9 +/- 4.7 vs 31.7 +/- 6.3 cmH2O, P = 0.007). This was consistent with a lower maximum tidal volume achieved with the LMAS (481 +/- 76 vs 515 +/- 63 ml, P = 0.044). We found that after 60 minutes the cuff pressure was significantly higher in the PLMA (110 +/- 21 vs 57 +/- 8 cmH2O, P < 0.001). There was no difference in the ability to provide adequate ventilation and oxygenation during anaesthesia. Complication rates were similar We conclude that the oropharyngeal leak pressure and the maximum achievable tidal volume are lower with the LMAS than with the PLMA.