Hereditary angioneurotic oedema is an autosomal dominant disease associated with serum deficiency of functional C1-inhibitor. It is characterized by periodic swelling of subcutaneous tissues, abdominal viscera and upper airways. Lethal acute episodes of oedema can occur during anaesthesia and surgery. It is essential to prepare such patients before surgery. This article describes three cases (kidney transplantation, caesarean section, normal delivery) and the various preventive measures used to avoid acute episodes during anaesthesia and surgery. Antibrinolytic agents, androgens, fresh frozen plasma, C1-inhibitor concentrate can be administered. Their various indications are discussed.