a procedure for removing high titer antibodies by extracorporeal proteinasepharose adsorption in hemophilia substitution therapy and surgery in a patient with hemophilia b and antibodies a 37yrold hemophiliac with factor ix antibody in high titer required operation for a pseudotumor growing invasively into the bone in his left elbow exchange plasmapheresis was not feasible mainly because of possible stimulation of factor ix inhibitor in addition the patient had antibodies against tissue antigens the factor ix antibodies were of igg type and adsorbable to proteinaagarose the antibodies were removed by extracorporeal adsorption of the plasma separated intermittently in a cell centrifuge to sterile proteinasepharose in columns operated by a computer the treated plasma was retransfused in this manner a total of 6000 ml of plasma was depleted of antibodies and the antibody titer as well as the total immunoglobulin content decreased to onefifth of the original values the remaining antibodies were neutralized by infusion of factor ix concentrate conventional substitution therapy in combination with immunosuppression was then possible the operation was performed without complications no signs of hemolysis complement activation or activation of the coagulation system occurred in principle the same form of treatment can be used in patients with other forms of antibodies