An aqueous solution of cysteine-altered von Willebrand Factor fragment which is substantially free of aggregate and capable of therapeutic use for treating thrombosis and a process for preparing such a solution comprising:(A) providing an aqueous solution of the fragment and denaturant;(B) purifying the solution of fragment and denaturant under conditions which promote conversion of aggregated forms of the fragment to the dimeric and/or monomeric forms thereof to provide purified fragment;(C) separating the dissolved, purified fragment from the denaturant while maintaining the aqueous solution of the fragment at a pH of about 2.5 to less than about 5.5 to increase monomerization of, and decrease aggregation of, said purified fragment, thereby forming an aqueous solution of fragment which is substantially free of aggregate.