Angioedema from angiotensin converting enzyme inhibitors: a cause of upper airway obstruction. Angiotensin-converting enzyme (ACE) inhibitors have several side effects of concern to the otolaryngologist. Angioedema is a rare, but potentially lethal adverse effect when associated with upper airway obstruction. Four cases of ACE-inhibitor-induced angioedema, three with significant upper airway obstruction, are reported. Angioedema secondary to ACE inhibition appears to be mechanism based. The probable link is the potentiation of bradykinin, which results in vasodilation, increased vascular permeability, and angioedema. Since angioedema can progress to upper airway obstruction, otolaryngologists must be aware of this association. The differential diagnosis and treatment of this adverse effect is discussed, as well as a review of ACE inhibitors and other causes of angioedema. 