Abstract XPS and SSIMS studies on the bonding of 3-methacryloxypropyltrimethoxysilane to the surfaces of different fillers, E glass, alumina, and quartz, have been performed. Qualitatively it has been found that the silane does not predominantly form a polymethacrylate on the surfaces of the fillers cited above, except for Quartz. It stands either upright or in horizontal layers and siloxane bridges between different molecules are probable. Using an approximated model the coverage and the thickness of the silane layers have been drawn from XPS intensities. It has been found that thickness is rather independent of both the experimental conditions of the treatment and the filler we used. Coverage is a function of both the experimental conditions and the filler. Using the maximum coverages for each filler and plotting them against the ratios of the calculated occupied area to the surface specific area of the filler, we observed a remarkable linearity. This suggests that, working with a deficiency of silane as we did, the yield of the silanization is essentially a function of the amount of added silane and of the specific surface area of the filler.