Use of plasma-enhanced chemical vapor deposition (PECVD) for electrochromic WO3 film deposition is investigated. Oxygen, hydrogen, and tungsten hexafluoride were used as source gases. Reactant gas flow was investigated to determine the effect on film characteristics. High quality optical films were obtained at deposition rates on the order of 100 Angstrom/s. Higher deposition rates were attainable but film quality and optical coherence degraded. Atomic emission spectroscopy (AES), was used to provide an in situ assessment of the plasma deposition chemistry. Through AES, it is shown that the hydrogen gas flow is essential to the deposition of the WO3 film. Oxygen gas flow and tungsten hexafluoride gas flow must be approximately equal for high quality films.