AbstractTwo similar techniques of red cell depletion of blood group-incompatible marrow prior to bone marrow transplantation were compared in 8 patients. me first method involved a single sedimentation step and removed a mean of 91% of marrow red cells and 33% of marrow nucleated cells. me second method involved multiple sedimentation steps and removed a mean of 96% of red cells and 29% of nucleated cells. Both methods can be recommended to a transfusion service newly involved in a bone marrow transplantation program.