The application of X-ray microanalysis, electron energy-loss spectroscopy (EELS) and the surface analysis techniques of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) to the characterization of materials is discussed. Examples of the application of these techniques to the characterization of amorphous films of silicon nitride, silicon carbide, hydrogenated carbon films and synthetic diamond films are described, Compositions obtained by each of these analytical techniques have been found to be in good agreement. The use of AES, XPS and EELS to investigate bonding and electronic structure in thin films and surfaces is discussed. Computer programs that have been developed to improve quantification in AES and XPS are described. These programs allow a comparison of matrix factor and final surface compositions obtained using different electron attenuation length corrections, back-scatter corrections and photo-ionization cross-sections. Computer programs involving Monte Carlo simulations of X-ray emission, which have been developed to enable quantification of the composition of thin films on thick substrates, are also described.