The detection of damage in fibre-reinforced composite materials is important in areas where these materials are used for load-bearing applications. This paper reports on the use of conventional reinforcing E-glass fibres that were made to act as light guides. These reinforcing fibre light guides were used to detect damage induced in the composite by impact, indentation and flexure. The E-glass fibres were converted into light guides by applying an appropriate cladding material. The coating resins used in this study were an epoxy- and a polyurethane-based resin system. These self-sensing fibres or reinforcing fibre light guides were surface mounted and also embedded at two specified locations within 16-ply glass fibre-reinforced epoxy prepreg composites. The data generated in this study demonstrated that the self-sensing concept could be used to study in situ and in real time the failure processes in glass fibre-reinforced composites. A detailed study was also undertaken to characterize the various failure modes observed when the composites with the self-sensing light guides were subjected to impact, indentation and flexural loading. The damaged areas in the composite were easily located by means of the 'bleeding' light emanating from the broken self-sensing E-glass fibres.