Patients with hemophilia A and circulating anticoagulant (factor VIII inhibitor) present a difficult, even unsolvable problem, particularly if they require surgical treatment and the inhibitor titer is high. During the 1986-1995 period 29 surgical procedures on inhibitor hemophilia A patients were performed in our center. Each of the cases had an individual character, and all demanded special clinical treatment. Based on this experience we present the possibilities of hemostasis maintenance during the perioperative period with high doses of human or porcine factor VIII, aPCC, plasmapheresis, and extracorporeal antibody adsorption to protein A-Sepharose. In some patients hemostasis maintenance requires combined treatment. To induce immunotolerance in patients with inhibitor is the gold standard treatment because it is then possible to achieve proper hemostasis after factor VIII infusion. Various methods of immunotolerance induction have been discussed and compared with our experience with immunotolerance induction in 11 patients with small factor VIII doses (25 IU/kg twice a week) and the modified Malmö protocol in 15 patients.