Three treatment arms are defined for the efficacy component of the study. (1) Subjects who are currently being treated on a set prophylaxis regimen with a VWF product at the time of study entry will be enrolled in the "Prophylaxis" arm. (2) Subjects not being treated on a set prophylaxis regimen at the time of study entry who require a VWF product for the treatment of NSB events will be enrolled in the "On-demand" arm and commence using Biostate in the treatment of NSB events. (3) Subjects enrolled in the "On-demand" arm have the possibility to enter the "Cross-over to Prophylaxis" arm to receive an additional 12 months of prophylactic treatment.