vWF is prepared from citrated human plasma using a combination of chromotographic procedures. Although the starting material was tested prior to initiation of the manufacturing process, and was found negative or nonreactive for anti-HIV-1/2, HIV-1 antigen(s), HBsAg, STS, anti-HCV, anti-HBcore and anti-HTLV I & II, extreme caution should be used when handling this material as there is a margin of error in all tests. This preparation is >95percent pure as judged by SDS-PAGE under reducing conditions, and consists of large multimers as determined by electrophoresis in SDS/agarose gels. Molecular weight under native conditions ranges from 520 kDa (dimer) to >10,000 kDa (multimers). Protein concentration determined by total protein assay. Required thawing procedure: Remove the sample from freezer and place in a 37 degree celsius water bath. Allow the vial to remain in the water bath for 2 minutes without agitation following complete disappearance of the frozen material. Remove sample and gently mix with a pipet or by gentle agitation. If precipitate is observed, place in water bath for an additional 2-3 minutes then mix again.