Wild-type full-length cDNA of von Willebrand factor (vWF) was expressed in CHO cells. Recombinant vWF (rvWF) was obtained and its molecular composition investigated by two-dimensional electrophoresis. Results of first dimension electrophoresis under non-reducing conditions showed that rvWF-dimer represents a mixture of three different species. Second dimension electrophoresis under reducing conditions revealed, that these protein species represent (i) homo-dimers of either two unprocessed or two fully processed, mature vWF polypeptides, and (ii) the hetero-dimer of unprocessed and mature rvWF monomers. Compared with vWF-dimers from human plasma, which contained predominantly proteolytically degraded polypeptides, recombinant vWF-dimers were shown to consist of non-proteolyzed subunits only.