It is currently unclear to what degree methylene blue in combination with removal, of cells from plasma, by filter, can directly influence the loss of active components of plasma and whether the co-precipitation of FVIII/vWf with fibrinogen/fibronectin is affected by combined methylene blue and light treatment (MBLT). These questions are investigated using the Fenwal system. Our results indicate that up to 15% of the FVIII and IX are lost due to exposure of plasma to filters and methylene blue (MB). The illumination leads to a further 10-15% loss of all other major clotting factors. Factor XI appears to be highly sensitive to the MBLT-process, while inhibitors of the coagulation system are less affected. MBLT did not grossly influence the distribution of fVIII/vWf:Ag between cryoprecipitate and cryosupernatant using a paired control/test protocol, although the fVIII/vWf recovery is reduced in MBLT samples. The three commercially available MBLT processes differ in terms of operational aspects. These may have some impact on overall quality/safety and bioequivalency.