Abstract: The present invention relates to an improved method for enzymatically removing blood type-specific antigens from erythrocytes, comprising titrating the pH of the erythrocytes first to a pH suitable for enzyme activity and then, once the desired extent of antigen removal has been achieved, to a pH appropriate for storage and/or transfusion. The buffers used for titration have pH values significantly above or below the target pHs for erythrocyte conversion or storage/transfusion. The invention is based, at least in part, on the discovery that the structural integrity of the erythrocytes is not substantially disrupted by titration. The present invention further relates to methods wherein the addition of polyethylene glycol improves the efficiency of enzymatic removal of erythrocyte antigens.