Hydrogen-free, hard carbon films prepared by a pulsed cathodic arc discharge method under different deposition conditions were investigated using Raman spectroscopy. The influence of a number of deposition parameters (discharge voltage, temperature and orientation of the substrate, admixtures, etc.) on the shape of the Raman spectra is considered. The maximum of the Raman intensity ratio R = I500/I1550 and the minimum of the slope S = (I1300-I1100)/I1100 are demonstrated to correspond to the highest diamond-like properties of the films. The numerical correlation of R and S with the sp3/sp2 ratio is established. The presented results show that the spectral parameters R and S are suitable for quantitatively characterizing films with an sp3/sp2 ratio larger than 0.3. © 1997 Elsevier Science S.A.