An essential prerequisite for CI is factor concentrate maintaining its extended stability in the clinical settings of its use, i.e. after reconstitution, in the reservoir of the infusion pump at room temperature. Extensive stability studies conducted in the early 1990s demonstrated that most plasma-derived concentrates (pdFVIII/FIX) available at that time remained stable for several days after their reconstitution, and sometimes even for weeks [1,11]. Subsequently, many new-generation products