This study provides data on the potential of using serum TNF-α levels in differentiating between high and low inhibitor levels in severe hemophilia A. This finding seems to support decision making on the treatment option of inhibitor in severe hemophilia A. Meanwhile, the frequency of replacement therapy was significantly different between low- and high-titer FVIII inhibitors regarding serum TNF-α levels. The gene discussed is TNF; the disease is hemophilia A.