The Essential Work of Fracture (EWF) theory has been applied to study the fracture behaviour of untreated and silane-treated glass bead-filled EPDM composites. The experimental values of both Young's modulus and tensile strength have been compared with those predicted by the main theoretical and semiempirical models, and the influence of the composite processing temperature on the tensile properties has been studied, noticing a marked drop of stiffness and strength from a processing temperature of 200 degreesC. A good adhesion between EPDM matrix and glass beads was achieved with the silane Z-6032, resulting in higher tensile strength, and it has been observed that glass bead presence induces plasticity in the EPDM matrix. No differences of the specific essential work of fracture were found in the three filled samples, although results show that the higher adhesion degree between matrix and particles, the higher value of the specific plastic work of fracture, and also the higher final instability in crack propagation.