A multicentre study to investigate the pharmacokinetics, clinical efficacy and safety of nanofiltered Cetor® (called C1-esteraseremmer-N during the development phase) for the treatment of hereditary angioedema (HAE) will be performed. This study (KB2003.01) consists of three parts: Part A - pharmacokinetics (phase II); Part B - treatment of attacks of angioedema (phase III); and Part C - prophylactic use of C1 inhibitor (phase III). Parts B + C will provide data on the efficacy of C1-esteraseremmer-N.