The recent developments in Auger spectroscopy have been used to define the composition of two glass fiber surfaces. The effect of fiber surface area on the interlaminar shear strength was also investigated. The chemistry of several silane “coupling agents” has been studied from the standpoint of its chemical form when it is applied to the glass fibers, and has in part been determined using a gas chromatographic technique. The relative thermal stability of some silanes in high temperature resin matrices was determined. A comparison of a treatment of glass fibers with aqueous and non-aqueous systems is made.