This work covers studies on interfaces between epoxy and recycled rubber used as toughening phase in epoxy resins. Different surface modification techniques were used to improve the compatibility at the interface between the rubber particles and the epoxy matrix. Silane coupling agents, plasma surface modification and acrylic acid/benzoylperoxide were used to enhance the surface properties of rubber particles. Rubber parts of grinded scrap car tyres with a size range of 355-500 mum after surface treatment were mixed with epoxy. This mixture was poured into molds to obtain fracture toughness test specimens. After curing, plain strain fracture toughness tests were performed and the fractured surfaces of the specimens were examined under scanning electron microscope. Fractographic studies indicated that the increase in fracture toughness values were due to the improved interface Leading to crack deflection as the main rubber toughening mechanism. Secondary rubber toughening mechanisms observed were shear deformations and some debonding initiated at the interface.