The pathogenesis of Menkes disease seems to be linked to metallothionein which binds to copper trapped within cells in some tissues. The only known therapy for this disease is parenteral administration of copper, but the effects are equivocal. We treated a patient with Menkes disease by giving vitamin C orally. The clinical manifestation and bone changes improved and the plasma copper and ceruloplasmin levels gradually increased. Vitamin C may prevent the binding of copper and metallothionein by its reducing effect, and excess copper would be released from the cells. Vitamin C treatment is a simple and physiological method, and should aid in clarifying the pathogenesis of the disease.