Hereditary Angioedema is an autosomal dominant disease characterized by abnormalities in Cl esterase inhibitor. We have previously shown that danazol corrected the protein abnormality in patients with this disease. During this year we have further extended observations of the usefulness of danazol and danazol toxicity in a large patient population. We have begun to characterize the incidence of autoimmune diseases in this patient group as well. Further, we have extended our experience with the use of purified Cl esterase inhibitor in the treatment of Hereditary Angioedema attacks and have shown that the therapy can abort these potentially life threatening attacks.