Background: Cough suppression is a well-known side effect of all opioid analgesics, but we experienced cough response after small dose of intravenous fentanyl. The goal of this study was to demonstrate the tussive effect of intravenous fentanyl. Method: 311 patients(ASA class 1, 2) were assigned randomly into three groups. Patient in group 1 recieved fentanyl 1 ug/kg, patients in group 2 were given fentanyl 2 ug/kg, and patients in group 3 recieved fentanyl 2 ug/kg 2 min after lidocaine 1 mg/kg. We observed for 1 min after fentanyl injection to detect a cough response. Results: Tussive response of fentanyl is produced by low dose (1-2 ug/kg) fentanyl IV, and decreased by lidocaine pretreatment. This response is decreased with aging. All event is not related bronchospasm and anticholinergic premedication. Conclusion: We concluded that fentanyl causes tussive response and this response is inhibited by lidocaine and decreased with aging. (Korean J Anesthesiol 1996; 31: 462~465)