Angiotensin-converting enzyme inhibitors (ACEI) are commonly prescribed for blood pressure control and renal protection. ACEI angioedema is a common problem in patients who are taking ACEI, although, in most cases, the disorder is self-limited, and spontaneous episodes of apparently unprovoked angioedema stop with the discontinuation of the medication. In a subset of patients, hospitalization and even intubation are required for airway protection. The diagnosis is made clinically. There are no laboratory studies that establish the diagnosis. However, such investigations help exclude alternative diagnoses as the cause for the patient's presentation. Conventional treatment with regimens used to control allergic angioedema is ineffective in this condition. The mechanism of ACEI-induced angioedema is thought to be related to its effect on the kallikrein-kinin system. Kallikrein is a protease that converts high-molecular-weight kininogens into kinins, primarily bradykinin. Medications recently developed, primarily icatibant and ecallantide, to control hereditary angioedema, a disorder also associated with kallikrein-kinin activation, have been used to treat ACEI angioedema with some success. The efficacy of these agents and their optimal use remains to be established by randomized and placebo controlled trials.