Proton insertion in polycryst. tungsten oxide has been studied with photoelectron spectroscopy and semi-empirical calcns. The W 4f spectra show growth of W5+ and W4+ oxidn. states as a function of inserted proton content in the crystal lattice. A concomitant growth of bandgap structure displays two sep. peaks. Semi-empirical calcns. using the periodic large unit cell (LUC) method suggest the growth of W4+ states based on the total energy variation with respect to the no. of protons/unit cell. At this stage the general picture of insertion is that of a multiphase system contg. regions of different x values.