Fresh frozen plasma (FFP), was shock-frozen to -25 degrees C within six hours after blood donation. The platelet count was reduced to 20 000/mm3. Aliquots were stored at -20 degrees C and -40 degrees C up to 24 months. Quick, PTT, factor V, VIII, IX, thrombin, antithrombin III, plasminogen, plasma-prekallikrein and kallikrein were determined monthly. With respect to the parameters investigated there was no significant difference between storage at -20 degrees C and -40 degrees C. Factor VIII loss was 10% after 12 months of storage. The activity of factor IX and V remained unchanged during 12 months, then factor V increased during storage. The other parameters did not change. Our study indicates quality of FFP seems not primarily depend on storage temperature, but an optimal preparation technique is much more important.