Background: Occasionally inserting a gastric tube in anesthetized or unconscious patients may be difficult or failed. Various techniques have been explained to resolve the problem. In a randomized clinical trial, we studied the efficacy and safety of a new method for orally gastric tube insertion in anesthetized patients.Methods: Along a 5-month period, 90 adult patients candidate of cardiac surgery randomly allocated in three groups due to methods of gastric tube insertion. Fifteen minutes after anesthesia induction, gastric tube was inserted nasally (NGT group, n=30), simply orally (OGT group, n=30) or orally via an uncuffed split endotracheal tube size 6.0 mm (ETT group, n=30). The success rate, time consumption, hemodynamic changes and complication rates were compared between three groups. Results: Two patients were excluded from the study, because of long intubation time. Demographic and preoperative characteristics were comparable between three groups. Hemodynamic changes due to procedure were not different. Time required for tube insertion in ETT group was significantly shorter than the other two groups (80.60 ± 66.132 sec versus 124.09 ± 100.055 and 139.77 ± 80.363 sec in NGT and OGT groups, respectively) (p=0.012). Success rate was significantly high in ETT group comparing to other two groups (100 percent in ETT group versus 77 and 86 percent in NGT and OGT groups, respectively) (p=0.008). The ETT method was used when procedure was failed in other two methods. Complication rates were not different between three groups and the most common complication was sore throat/odinophagia (17%). Hemorrhagic problems were seen in 5, 3 and one patient in NGT, OGT and ETT groups, respectively.Conclusions: Using a split endotracheal tube, as a guide tube, is an effective, fast and safe method for orally insertion of a gastric tube in anesthetized or unconsciousness patient.