BACKGROUND Hereditary angioedema results from the deficiency of C1-esterase inhibitor (C1-INH), and C1-INH replacement would represent definitive treatment for angioedema attacks. In Canada, C1-INH is available only on a compassionate basis at select medical facilities. Our objective is to assess the efficacy of C1-INH transfusions during angioedema attacks at a single Canadian institution. METHODS A retrospective chart review of transfusion data between January 1, 1995 and June 30, 1996 was performed. Phone interviews with patients elicited their opinions of the treatment. Data collected included the number and duration of angioedema attacks, dose of transfused C1-INH, and side effects of treatment. RESULTS Of a cohort of 13 patients with hereditary angioedema, seven received transfusions with C1-INH. Attacks totaled 87, and more than 100,000 units of the product were transfused. The mean time for abatement of an attack after initiation of transfusion was 50 +/- 8 minutes (1 SD). There were no reports of adverse effects. Although patients were satisfied with the treatment, they raised concerns regarding long-term safety and availability. CONCLUSIONS C1-INH transfusion is a satisfactory means of treating angioedema attacks.