This present investigation tests the efficacy of the self-inflating bulb for detecting esophageal intubation after intentional “esophageal ventilation” to mimic gastric insufflation after bag-and-mask ventilation. In 72 anesthetized patients, the trachea and esophagus were intubated with identical tubes. The efficacy of the bulb was tested by a second anesthesiologist before and after the delivery of three breaths at a tidal volume of 300–350 mL each. The pressures generated by the bulb connected to esophageally placed tubes were measured in 10 patients. In all patients, the second anesthesiologist reported no reinflation of the bulbs when connected to esophageally placed tubes and instantaneous reinflation when connected to tracheally placed tubes, thus correctly identifying the location of each tube. The mean negative pressure generated when compressed bulbs were connected to esophageally placed tubes was 55.4 ± 1.2 mm Hg before esophageal ventilation and 59.0 ± 0.68 mm Hg after esophageal ventilation. We conclude that insufflation of the stomach as a result of esophageal ventilation, to the extent demonstrated in this study, does not interfere with the effectiveness of the bulb in differentiating esophageal from tracheal intubation.