The purpose of this study was to report the results of different treatments in 20 patients with hereditary angioedema. Effectiveness of tranexamic acid in preventing swellings was evaluated in 15 patients: in all but 3 subjects tranexamic acid was effective without serious side effects. 15 severe attacks of edema were managed with intravenous infusions of either kallikrein inhibitor (8 cases) or concentrate of C1 esterase inhibitor (7 cases). In only 1 case was the kallikrein inhibitor unsuccessful. C 1 esterase inhibitor concentrate proved highly effective in the treatment of acute attacks (the result was lacking in one patient because of too low dosage of the drug). No side effects were observed with both treatments, but improvement was more rapidly achieved with infusion of C1 esterase inhibitor. The serum levels of C4 and C1 esterase inhibitor and the activity of C 1 esterase inhibitor before and after long-term prophylaxis and acute attacks treatment were investigated.