 In part A, the pharmacokinetics of C1-esteraseremmer-N in patients with hereditary angioedema will be compared with the current registered product, Cetor, in a randomised, blinded cross-over design. This study has to provide evidence that changes in the manufacturing process have not affected pharmacokinetics. In addition, this study provides data on safety of C1-esteraseremmer-N. Twelve HAE patients without signs of an attack will receive an administration of 1,000 U, 1,500 U or 2,000 U of C1-esteraseremmer-N or Cetor and later on the same dose of the other product. Both antigenic and functional C1 inhibitor levels will be determined. Laboratory safety parameters and adverse events will be monitored as well 