Hereditary angioedema is a rare genetic condition transmitted as an autosomal dominant trait and characterized most commonly by the production of either inadequate or nonfunctioning C1 esterase inhibitor (C1-INH), a blood protein that regulates proteases in the complement, fibrinolytic and contact systems. Patients with hereditary angioedema suffer from episodic, unpredictable manifestations of edema affecting multiple anatomical locations, including the GI tract, facial tissue, the upper airway, oropharynx, urogenital region and/or the arms and legs. A rational approach to treatment is replacement of C1-INH protein, to normalize the levels of C1-INH activity and halt the progression of the biochemical activation processes underlying the edema formation. Ruconest is a highly purified recombinant human C1-INH. This article will focus on the results of ten clinical studies demonstrating the efficacy and safety of Ruconest(®) (Pharming Group NV, Leiden, the Netherlands), which is now approved for use in Europe, Israel and the USA.