In hemophilia, an X-linked recessive disorder, women whose fathers have hemophilia are carriers. This report describes the results of administering clotting factor products to 2 confirmed carriers with low levels of coagulation factor VIII/IX (FVIII/FIX) activity whose fathers were hemophilia A and B patients, respectively. Case 1 was a 3-year-old girl. The patient visited the orthopedic department with a chief complaint of joint swelling, but the symptoms did not improve. Since bleeing in the knee joint and low FVIII activity were confirmed during the initial visit to our hospital, rFVIII preparation was administered and the swelling and pain in the knee joint improved. Though the joint bleeing was repeated, it was not observed since the start of prophylactic factor replacement therapy. Case 2 was a 39-year-old woman. The patient visited the hospital at 16 weeks of gestation. Although she showed low FIX activity, she delivered by cesarean section due to bleeding control by administration of rFIX preparation. It was possible to deal with the urgent cesarean section by examining the dose beforehand in the preliminary trial administration. In these cases, it was suggested that assessment of coagulation factor activity in confirmed carriers would enable appropriate management of symptoms.