A total of 83 subjects were enrolled in the study. Seventy-one (71) subjects experienced qualifying attacks and were randomized to blinded study drug (36 C1INH-nf, 35 placebo); only the 71 randomized subjects were analyzed for efficacy. An additional 12 subjects were never randomized but received open-label C1INH-nf for treatment of laryngeal angioedema and/or prior to emergency surgical procedures. Of the 35 subjects randomized to placebo, 23 also received C1INH-nf (eg, rescue, open-label). In total, 83 subjects received at least 1 dose of study drug and were analyzed for safety; 71 subjects were exposed to C1INH-nf (59 randomized, 12 open-label only) and 12 subjects were exposed only to placebo.