Little is known about the potential for the cuff of the ProSeal laryngeal mask airway (PLMA) to cause laryngopharyngeal mucosal injury. The aim of this study was to investigate the effects of prolonged exposure of the laryngopharyngeal mucosa to the PLMA in an animal model. The PLMA was used for positive pressure ventilation in eight German country pigs randomized to receive different durations of anesthesia lasting three to 24 hr. Two additional pigs served as controls. Biopsies from 14 predetermined areas of the laryngopharyngeal mucosa were examined histopathologically using light microscopy. The number of areas with signs of mucosal damage was evaluated, and the degree of tissue damage was analyzed using a semiquantitative scoring system. The number of areas with moderate to severe mucosal damage was 0-2 in animals anesthetized for less than 12 hr, 6 in animals anesthetized for 12-18 hr, and 12 in animals anesthetized for more than 18 hr. The severity of mucosal damage was also time-dependent, indicated by raising semiquantitative scores for epithelial and subepithelial mucosal damage. The histopathological findings of this study show that prolonged use of the PLMA in the pig for up to nine hours is associated with no, or only mild alterations in the laryngopharyngeal mucosa, whereas use for 12 hr or more is associated with clear signs of mucosal injury.