From mid-1967 to mid-1983, three hundred fifty surgical operations were performed on 163 patients with hemophilia A, without factor VIII inhibitor. One death occurred, in a patient with a serious head injury. Postoperative hemorrhages occurred after 23% of operations, but the incidence after surgery on the knee, 40%, was decidedly higher than the 15% incidence after operations at other sites. Concurrent plasma factor VIII levels were over 0.40 units/mL in 72% of instances and under 0.30 units/mL in only 15% of instances. The incidence of postoperative hemorrhage did not change over the study period despite a threefold increase in typical dosage of factor VIII (from 600 to 2,000 units/kg per operation) and doubling of typical trough factor VIII levels (from 0.37 units/mL to 0.70 units/mL). Circulating factor VIII levels apparently are not the sole determinants of postoperative bleeding in hemophilia A.