We have compared the performance of the single use laryngeal airway devices Softseal and LMA-Unique in a randomised comparative trial in anaesthetised healthy patients who did not receive neuromuscular blockade. Primary outcome was success of airway placement. Secondary outcomes included manipulations and complications during use, ease of insertion, airway and fibreoptic assessment of airway positioning, and complications postoperatively. We planned to study 300 patients but interim analysis demonstrated the study should be stopped after 100 patients. During insertion the Softseal required more attempts for successful insertion (p = 0.041), more manipulations (p < 0.0001) and caused more complications (p = 0.048). Failure of placement occurred in five cases with the Softseal and none with the LMA-Unique (p = n/s). Two Softseal needed to be removed during maintenance because of airway obstruction, giving an overall failure rate of seven (p = 0.013). Serial tests of positioning favoured the LMA-Unique (p = 0.012). Ventilation was more successful in the LMA-Unique group but the difference was not significant (p = 0.051). Seal pressure was higher with the Softseal (26.5 vs. 20.5 cmH(2)O, p = 0.005). Fibreoptic view via the devices was not statistically significantly different. During maintenance of anaesthesia more complications arose with the Softseal (p = 0.03). Anaesthetist ratings of ease of insertion and overall usefulness favoured the LMA-Unique (p < 0.0001 and p = 0.024, respectively). After anaesthesia, sore throat occurred more frequently and was more severe in those patients anaesthetised with a Softseal both in recovery (p = 0.015) and at 24 h (p = 0.012). We conclude that the Softseal performs less well and causes more complications than the LMA-Unique.