Hereditary angioedema (HAE) is an autosomal dominant disease characterized by deficiency of C1 inhibitor (C1-INH) that commonly presents with recurrent swelling affecting different parts of the body. Supplementation with C1-INH is successfully used to treat HAE in selected countries, mostly in Europe. Berinert P (CSL Behring, Marburg, Germany), a human plasma-derived C1-INH, was studied in the International Multicenter Prospective Angioedema C1-inhibitor Trial 1 (IMPACT1) that was completed in 2007. It was the first safety and dose-finding study of C1-INH in patients with acute abdominal and facial angioedema. IMPACT2 was the extension of the first trial to study C1-INH efficacy and safety in multiple treatments of acute HAE attacks in various areas of the body. Berinert P has excellent potential to become a first-line therapy for treating patients with acute HAE attacks in the USA and other countries involved in the IMPACT trials. While final data from the IMPACT2 trial are not yet released, this article reviews currently available data from previous reports and abstract presentations.