A total of 7 families with hereditary angioneurotic oedema (HANE) have been found in Finland. Six HANE patients have died from laryngeal oedema, 27 patients with diagnosed HANE are alive and 21 members have a haematological abnormality typical of HANE, i.e. a deficiency of the inhibitor of the activated first component of complement (C1-INH), but no manifest symptoms. The largest family has 363 living members, 303 of whom were investigated for C1-INH, C4 and C3. Fourteen patients had HANE, 18 relatives were symptomless but had C1-INH deficiency, and 3 members of the family had died from laryngeal oedema. In two families only one case of HANE was diagnosed, the parents in both cases being symptomless with normal C1-INH levels. All patients who had died from laryngeal oedema and 10 of the 27 HANE patients still alive had a typical triad of paroxysmal abdominal pain, peripheral oedema and laryngeal oedema. Six patients have had abdominal attacks alone, three peripheral oedema alone and two only laryngeal oedema. The age at onset of symptoms was 1-51 years. Three patients, who have received continuous methyltestosterone therapy, had hardly any symptoms during the treatment. Thirteen patients have received tranexamic acid, either during an attack or continuously, with positive effects in all except two. Cinnarizine treatment was beneficial in three out of four cases, both when given continuously or during an attack.