X-ray diffraction (XRD) and spectroscopic ellipsometry measurements have been performed to study the crystalline structure of polycrystalline silicon films deposited by cathode-type r.f. glow discharge. Ratios of XRD peak intensities are used to describe the degree of crystallinity of samples. For ellipsometric data analysis, a multilayer structure model is used based on the effective medium approximation. It is found that the crystalline fractions of the deposited films increase with the increase of power density and substrate temperature. The film compositions of as-deposited samples are compared with those of annealed samples and films prepared by thermal pyrolysis of silane. The crystallinity estimated from the ellipsometric measurements compares well with that obtained from XRD measurements.