Angioedema is a rare but potentially serious adverse event of angiotensin-converting enzyme inhibition. However, there are no prospective, controlled studies on its incidence and clinical characteristics. Kostis et al studied the occurrence of angioedema in a randomized, double-blind, controlled trial of 12 557 persons with hypertension treated with enalapril maleate, 5 to 40 mg daily, using a prospective ascertainment and adjudication of angioedema by an expert committee. Although it was more likely to occur early after initiation of therapy, angioedema could also occur at any time. It was more likely to occur in blacks, patients older than 65 years, and those with a history of drug rash or seasonal allergies. Fatal angioedema or angioedema requiring airway protection did not occur in this study.