Amorphous Si : C : N : O : H films (1-3 #m) are studied by EPMA after deposition of gold (1-5 nm) as a conductive coating. Its influence on the k-ratios (X-ray intensity relative to an uncoated standard) of silicon, carbon, nitrogen and oxygen is described as a linear function of the simultaneously determined k-ratio of gold. The k-ratios representing the uncoated specimen are obtained by extrapolation and, in combination with the PAP matrix correction model, quantitative EPMA can be performed with an analytical error of 2-5%, as it is demonstrated by samples of SiC, Si3N 4 and SiO 2. No systematic shift of the concentrations is observed for layers ofa-Si : C : N : O : H determined at various electron energies of 5-12.5 keV. Hydrogen is calculated by difference and the concentrations prove to be a useful estimate in agreement with the results of chemical analysis. Si-K~/Si-Kfl' spectra recorded on organo-silicon films and binary silicon compounds point out significant differences concerning the formation of Si-C, Si-N and Si-O chemical bonds.