Angioneurotic edema is a rare (0.1-0.2%) but potentially life-threatening side effect of angiotensin-converting enzyme inhibitors. It can result in serious respiratory distress, airway obstruction and death. Angiotensin-converting enzyme inhibitors associated angioedema is clinically poorly recognized and frequently underestimated condition. A case history of patient with angioneurotic edema due to treatment with ramipril is presented. A 51-year-old man has been sequentially treated for two years with atenolol, indapamide, enalapril, and fosinopril due to primary arterial hypertension. When the treatment was switched to ramipril 5 mg twice a day the fourth dose of the drug was followed by swelling of lips, tongue, and pharynx without symptoms of airway obstruction. Ramipril was discontinued, prednisolone 120 mg and loratidine 10 mg were given. Symptoms of angioedema gradually disappeared. Mechanisms of angioedema are not fully clear. Pharmacological action of angiotensin-converting enzyme inhibitors on bradykinin and substance P, immunological mechanisms and disarrangements in complement system are discussed. Treatment includes immediate withdrawal of angiotensin-converting enzyme inhibitors and acute therapy with epinephrine 0.3-0.5 ml subcutaneous, 50 mg diphenhydramine s/c or i/v, 40-50 mg methylprednisolone. Future treatment with angiotensin-converting enzyme inhibitors is contraindicated.