Hard a-C(N):H films were deposited onto Si(100) substrates by r.f. self-bias glow discharge in CH,-NH, atmospheres (NH, content varying from 0% to 12.5%). The chemical composition of the films was determined by nuclear techniques: and the film structure was monitored by IR and Raman spectroscopies. The nitrogen incorporation into the films was found to be more than four times greater than that previously obtained with N, gas as the nitrogen source at the same partial pressure. Nitrogen incorporation up to levels of 11 at.% resulted in a 50% decrease in the internal compressive stress. Raman spectra showed that nitrogen incorporation increased the size or number of graphitic domains in the film, while exhibiting smaller changes in the Id/Ig, ratio. IR spectra showed the same trend as observed in N2-derived films, with an increasing presence of nitrogen-containing network terminating groups at the expense of C-H groups.