This paper has three principle thrusts : (i) the fabrication of unidirectionally reinforced composites made from carbon fibres subjected to different surface treatments in combination with various (polycarbonate, polyethersulphone and epoxy) matrices, (ii) a study of some of the mechanical properties (that is, the interlaminar-shear strength (ILSS) and the failure behaviour) of these composites; and (iii) determination of the correlations between the adhesion of the matrix polymers as measured by the ILSS and the surface structure as well as the surface chemistry of the various fibres. It will be shown that the surface structure of the fibres has a minor effect, while the surface chemistry appears to have an extraordinarily great influence on the adhesion of the fibres to high-temperature thermoplastics. The data clearly show that, depending on the processing temperature during the fabrication of the composites, chemical bonds can be formed at the fibre-polymer interface. This bond formation is initiated by the decomposition of carboxylic groups and, as a consequence, dangling carbon atoms are free to react with the functional groups of the polymer.