1. Nowadays, it is possible to control the coagulation defect of hemophilia b to such an extent that normal hemostasis occurs even after major surgical procedures or severe injuries. The basis for normal wound healing is thus created. This is due to a) a rapid method for the determination of factor-ix which is reliable with meticulous technique and b) a non-toxic, non-pyrogenic and non-antigenic plasma fraction which contains a high concentration of factor ix (e.g. Ppsb). 2. On the basis of metabolic tests in healthy and ill humans and on the basis of having treated 3 patients with hemophilia b we were able to calculate that in order to achieve and maintain a 1% factor-ix-activity in the blood a loading dose of 1.2 ml(=1.5 ml of acd-plasma equivalents) per kg and a maintenance dose of 0.6 ml(=0.75 ml of acd-plasma equivalents) per kg of net fresh plasma equivalents should be administered per day (this is somewhat more than the amounts stated by us in 1961 on the basis of preliminary results). In patients with an increased catabolic rate one must expect to administer considerably higher maintenance doses and in these cases one should always base treatment on the course of the factor-ix-activity. The factor ix should be determined twice a day, always before a ppsb-injection is given. 3. A factor-ix-activity of 40% for the first 3 days after the injury, 30% in the next 4 days and 25% for another 4 to 6 days are desirable for optimum healing of large wounds. 4. Form the point of view of adequate substitution therapy of hemophilia b and of more economical use of human transfusion blood the production of a ppsb-like coagulation factor concentrate must be strongly recommended for every larger blood-bank.