Recombinant protein complexes having human Factor VIII:C activity are expressed in a eukaryotic host cell by transforming the host cell with first and second expression cassettes encoding a first polypeptide substantially homologous to human Factor VIII:C A domain and a second polypeptide substantially homologous to human Factor VIII:C C domain, respectively. In the present invention, the first polypeptide may be extended having at its C-terminal a human Factor VIII:C B domain N-terminal peptide, a polypeptide spacer of 3-40 amino acids, and a human Factor VIII:C B domain C-terminal peptide. Expression of the second polypeptide is improved by employing an .alpha.sub.1-antitrypsin signal sequence.