The electrochromic behavior of amorphous WO3 films prepared by electron-beam deposition has been studied. SIMS analysis has revealed that lithium accumulates in amorphous WO3 films during reversible coloring and bleaching in propylene carbonate solution of LiClO4. When a large quantity of lithium has been injected into WO3 films, an absorption spectrum different from tungsten bronze is observed. In these films, lithium tungstate has been observed using x-ray photoelectron spectroscopy and x-ray diffraction analysis. It has been concluded that the degradation of electrochromism of amorphous WO3 is caused by the formation of stable lithium tungstate. © 1990, The Electrochemical Society, Inc. All rights reserved.