WNx films have been deposited by reactive d.c. diode sputtering in an Ar-N-2 gas mixture on Si substrates. The electrical resistivity, structure. microstructure and composition of the films were investigated. The parameters were the total and partial pressures, the discharge current and the negative bias voltage applied to the substrate. We have found that good W2N films are obtainable with a dense structure and a resistivity of near 200 mu Omega cm, but either the resistivity or the composition and structure suffer great variations with the discharge parameters. Defending on the nitrogen partial pressure and the bias voltage, the deposited layers are W2N films, W2N-W mixtures or W films.