The appearance of antibodies to factor VIII is a serious complication in the treatment of haemophilia A. A protocol is presented aiming at suppression of the anticoagulant using continued treatment with factor VIII (25 u/kg b.w. twice weekly). Ten patients with previous maximal factor VIII antibody titre from 7 to 2900 Bethesda units were treated. So far the inhibitor was eradicated in 3 cases treated continuously for from 5 to 20 months. In two of these three cases successful surgical procedures were performed without anamnestic response.