In patients with excessive blood loss, coagulation is compromised by hypothermia, metabolic acidosis due to impaired tissue perfusion, loss of coagulation factors and platelets while their consumption is increased, and by massive infusion with plasma expanders. Currently available laboratory tests are insufficiently reliable and too time-consuming to enable the evaluation of the effect of pharmaco-therapeutic interventions during severe blood loss. Several haemostatic drugs appear to be effective in the treatment of blood loss after elective surgery, but have been insufficiently investigated in patients with severe bleeding. A rational transfusion policy entailing the use of sufficient amounts of plasma is necessary in the treatment of patients with severe bleeding.