The surface of glass fibres was modified using chemical treatments to im prove fibre-matrix interface properties. Interfacial polycondensation was performed with the fibre acting as the interface, and nylon-6,6 chains were grafted on the free hydroxyl groups located at the fibre surface. Grafted nylon was observed through the scanning electron microscope. The effect of the treatment on the fibre-matrix adhesion was investigated by measuring the interfacial shear strength in fragmentation micromechanical tests. The two-parameter Weibull distribution was used to analyse the experimental results. Polarized optical microscopy showed the existence of a transcrystalline layer in treated samples, indicating better fibre wettability by the matrix. Scanning electron microscopy confirmed the presence of an excellent bonding between fibre-and matrix in treated samples, whereas in untreated samples, fibre pull-out was predominant, indicating poorer fibre-matrix adhesion.