BACKGROUND: There were several studies for the incidence of gastroesophageal reflux associated with the laryngeal mask airway (LMA), but the results of those studies were much different from one another. This conflicting results may be due to the time of the removal of LMA, which has been usually after the arousal (when the patient can open the mouth on command). So, the authors investigated the incidence of the gastroesophageal reflux and the regurgitation of gastric contents above the upper esophageal sphincter associated with the difference of the time of the removal of LMA. METHODS: Sixty three patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were allocated randomly to Group A (n=34, LMA was removed when the rejection signs such as struggle, restlessness, swallowing and cough came out.) or Group B (n=29, LMA was removed after arousal). For the detection of reflux and regurgitation episodes during anesthesia, a pH monitoring probe was positioned in the lower esophagus and a methylene blue (50 mg) gelatine capsule was swallowed just before induction. At the end of anesthesia, the episodes of reflux and regurgitation of gastric contents were analyzed according to the pharyngeal blue staining or pH< or = 4. RESULTS: The incidence of reflux (pH< or = 4) from the time of the rejection signs to the removal of LMA and the total incidence of reflux in Group B were significantly higher than that of Group A. No patient in both group showed pharyngeal staining of methylene blue. There was no clinical evidence of aspiration of gastric contents in either group. CONCLUSION: Maintenance of LMA until the patient can open the mouth on command seems to increase the incidence of the gastroesophageal reflux.