Amorphous B4C and BC2N films were prepared on (1 1 1) silicon substrates by reactive laser ablation using a B4C target. For the depositions of BC2N a nitrogen pressure of 63 mTorr in the growth chamber was used. The electron inelastic mean free path (IMFP) for B4C and BC2N was calculated for energies between 200 and 2000 eV from their respective energy-loss functions, which was obtained from quantitative analysis of REELS. The IMFPs are analyzed in terms of the Bethe equation for inelastic scattering of electron. REELS results were used to obtain the dielectric function of the B4C and BC2N in the energy range from 4 to 100 eV.