The role of nitrous oxide in postoperative emesis is controversial. This prospective randomized study was performed to compare the emetic sequelae and quality of recovery between a group of patients anesthetized with propofol alone and a group anesthetized with propofol plus nitrous oxide. Seventy patients, ASA grade I or II, scheduled for ambulatory gynecologic laparoscopy under general anesthesia were included. Most factors which could influence the incidence of postoperative emesis were controlled. The overall incidence of emetic sequelae during the first 24 h postoperatively was 25% in the group anesthetized with propofol alone versus 29% for the group anesthetized with propofol and nitrous oxide. The incidence of emetic sequelae requiring therapeutic intervention was 13% and 6%, respectively. This difference was not statistically significant. The group of patients who received propofol alone required an average propofol dose of 221.5 +/- 71.9 micrograms.kg-1.min-1 to maintain anesthesia compared with 162.5 +/- 43.9 micrograms.kg-1.min-1 for the group receiving propofol plus nitrous oxide (P < 0.001). The time from discontinuation of propofol to eye-opening and orientation was significantly longer in patients anesthetized with propofol alone. Otherwise, the recovery variables were comparable between the two groups. We conclude that supplementing propofol with nitrous oxide in patients undergoing ambulatory laparoscopy reduces the requirements of propofol, expedites immediate recovery (emergence), and does not increase the incidence of postoperative emesis. This tends to confirm that there is no clinical advantage to omitting nitrous oxide.