Appendectomy was safely performed in a 9-year-old boy with classic hemophilia, and hemostasis was achieved by the use of cryoprecipitated human antihemophilic globulin therapy begun preoperatively and continued for 17 days. Except for urticaria, the use of cryoprecipitated factor VIII was entirely free of side effects. Cryoprecipitated factor VIII is unique among all factor VIII concentrates prepared heretofore in that it is a by-product of plasma fractionation. It may be simply and economically prepared in any blood bank geared to plasma fractionation procedures and may be stored for months without loss of potency. As such cryoprecipitated factor VIII is soon expected to become generally available. The broad clinical use of a potent human factor VIII concentrate holds promise of further reducing the risk and morbidity of bleeding in hemophilia and of permitting safe elective as well as life-saving surgery.