We report a case of intravenous ephedrine administration that abolished suspected bronchoconstriction during general anesthesia in a patient undergoing beta-adrenergic blocker therapy for hypertension and who was subsequently diagnosed postoperatively as having bronchial asthma. A 54-year-old man who had childhood asthma was scheduled for laparoscopic cholecystectomy at our institution. The preanesthetic interview suggested full resolution of his childhood asthma. His capnogram showed an airway obstructive pattern immediately after the initiation of mechanical ventilation. However, after administration of ephedrine due to low blood pressure during surgery, his obstructive capnogram reverted to normal. On postoperative day 3, he was diagnosed as having bronchial asthma. Furthermore, we found that small airway obstruction as indicated in his preoperative pulmonary function test (PFT) had been overlooked. Two important points arise from this case. First, the use of beta-blockers for the treatment of hypertension in patients potentially having obstructive lung disease should be avoided. Second, clinicians should carefully check the preoperative PFT results in detail to ensure that nothing has been overlooked.