Hydrated hydrogen vanadium bronze, H1+xV3O8.nH(2)O, prepared by ion-exchange reaction of Li1+xV3O8 with aqueous acids, was investigated with respect to the formation process. The relationship between the phase and the chemical composition of the ion-exchanged product was revealed. The structural properties of H1+xV3O8.nH(2)O were studied and its lithium insertion behaviour was examined to clarify its suitability as a lithium insertion host.