For each subject, only a single abdominal or facial attack was treated and evaluated. After receiving treatment, subjects were observed for a minimum of 4 hours, after which they could be discharged from the study center if they reported onset of symptom relief. Starting from 4 hours after treatment, subjects who reported insufficient or no symptom relief could receive a second dose of double-blind treatment (called "rescue medication") as follows: C1-INH 20 U/kg bw for subjects initially receiving placebo, C1-INH 10 U/kg bw for subjects initially receiving C1-INH 10 U/kg bw, and placebo for subjects initially receiving C1-INH 20 U/kg bw.