Hereditary angioneurotic edema results from the deficiency of C1-esterase inhibitor. The clinical picture of this autosomal dominant disorder is characterized by recurrent attacks of edema formation in the subcutis and/or the submucosa. The clinical records of 21 children with established hereditary angioneurotic edema were reviewed. Follow-up care included laboratory check-ups and abdominal ultrasound. Clinical manifestations of the disease first occurred in 2.5 to 12 years of age. Mechanical trauma was the most common precipitating factor. Pedigree-analysis revealed 19 patients with afflicted relatives. Long-term prophylaxis was initiated with tranexamic acid and danazol in 10 cases; 2 children required short-term prophylaxis. Therapy improved serum complement parameters significantly and reduced the frequency and severity of clinical manifestations. Acute, life-threatening edematous attacks were treated by the administration of C1-inhibitor concentrate, which achieved the resolution of the edema within several hours. Abdominal ultrasonography performed during the attack invariably demonstrated transitory ascites that resolved spontaneously after treatment. Adequate prophylaxis and follow-up care can spare pediatric patients from edematous attacks. Undesirable adverse effects can be avoided and the patient's quality of life can be enhanced considerably by administering the lowest effective drug dose.