Hereditary angioedema (HAE) is due to a deficit of the C1 inhibitor (C1 INH) of a dominant autosomic inheritance. Seven patients are presented from a family with HAE, four of whom with poor prognosis due to the frequency and site of the angioedema. Prophylaxis was obtained with long-term danazol since antifibrinolytic drugs are not efficient in the prevention of outbreaks of angioedema. In three cases a concentrate of C1 INH was administered and in another as short term prophylaxis prior to surgery. C1 INH was more efficient under these indications than fresh plasma or antifibrinolytic drugs.