We report a unilateral hypoglossal nerve paralysis following the use of a laryngeal mask airway in a 62-year-old woman with rheumatoid arthritis undergoing a shoulder joint replacement. Cervical epidural anaesthesia was combined with general anaesthesia using nitrous oxide administered via a laryngeal mask airway with the patient in the right lateral decubitus position. The next morning, the patient was noted to have a right hypoglossal nerve palsy. Compression of the nerve between the laryngeal mask airway cuff, distended with nitrous oxide, and the hyoid bone, was considered to be the cause of the nerve paralysis.