This work covers studies on systems with car tire regrind used as the 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 ground used car tires, with or without surface treatment, were mixed with epoxy. This mixture was poured into molds to obtain mechanical test specimens according to ASTM standards. After curing, mechanical tests were performed and the fractured surfaces of the specimens were examined under Scanning Electron Microscopy. SEM. Throughout the studies, changes in mechanical properties were followed by an increase in the volume percentage of rubber particles and by the effect of different surface treatment processes applied on rubber. A decrease in tensile properties and impact resistance was observed in general as compared to unmodified epoxy. On the other hand, slight increases in fracture toughness values were observed in all surface treated cases.