Patients admitted for day-case laparoscopy were assigned randomly to receive nitrous oxide-oxygen or oxygen, with enflurane, during a standard anaesthetic technique. Postoperative morbidity, in particular nausea and vomiting, and ability to resume normal activity were assessed over the ensuing 48 h. Supplementary administration of propofol during the operative procedure was required significantly more often (P less than 0.05) in the absence of nitrous oxide. There was no significant difference in the incidence of vomiting before discharge when nitrous oxide was omitted. The incidence and severity of nausea over the 48 h following operation was similar in both groups. There was no difference in analgesic or anti-emetic requirements before discharge and the time taken to resume normal activity was similar. It is concluded that nitrous oxide may be avoided readily in day-case laparoscopy without affecting postoperative morbidity or time taken to return to "street fitness" and normal activity.