In hemophilia patients receiving factor VIII (FVIII) or factor IX (FIX), either as prophylaxis or treatment, sometimes the immune system label them as foreign bodies with consequent antibody development which reduce effectiveness. Those are time dependent inhibitors and are influenced by genetics. The aim of the study was to measure FVIII and FIX inhibitors presence in 104 patients, 1 to 59 years old, that had received commercial lyophilized factors. Moderate hemophilia “A” was identified in 34,6 % of FVIII treatment patients, severe in 23,08 %, and mild in 13,4 %. While moderate hemophilia “B” was present in 2,88 % of cases. In addition, six Von Willebrand’s disease patients (5,77 %) receiving FVIII were included likely response to desmopressin treatment was not effective. The 20,29% of FVIII receiving patients were unable to name their pathology. The 40,8% of Bethesda tests were positive, five patients showed values above 5, that label them as “high respondents”. It is clear the need to perform Bethesda test as routine test in patients receiving lyophilized plasm.