Most patients with hereditary hemochromatosis are homozygous for C282Y in the HFE gene in populations of Celtic origin, but the genetic cause of this disease is unknown in Japan because of its rarity. A 48-year-old Japanese patient was recently diagnosed with idiopathic hemochromatosis. Analysis of the entire coding region of the patient's HFE by RT-PCR showed a heterozygous nucleotide substitution at nucleotide 527 from C to T, which resulted in A176V amino acid substitution. Another mutation at nucleotide 942 from T to C was observed, but this was a nonsense mutation. C282Y and another mutation, H63D, were not found in the patient. The mutation may have a possible role on the cause of hemochromatosis in this Japanese case.