Most polymer blends are immiscible and need to be compatibilized. Compatibilization can be accomplished either by addition of a compatibilizer or by reactive processing. Grafting has been the most common method for compatibilizing two immiscible polymers during reactive processing. In this work, the reactive blending of EPDM (ethylene- propylene-diene monomer) rubber and san (styrene-acrylonitrile) copolymer was studied. The blends were prepared in an internal mixer with three types of organic peroxides as initiator. The effects of initiator type and concentration, EPDM content, and mixing sequences of components were investigated. Blends were separated to their structural components (i.e., san, EDPEM, san-g-EPDM, and gelled EPDM) which were then characterized by FTIR spectroscopy and SEM microscopy techniques. Mechanical properties including tensile and impact strength as well as elongation-atbreak were measured. From the three initiators used, the blends which have 2,5- dimethyl-2,5-di-(t-butyl peroxy) hexane as initiator show better mechanical properties. Also, SEM studies reveal a good compatibility for san/EPDM blends using this initiator. The blend using 40 wt% of EPDM of the mentioned initiator contains 16.24 wt% sang- EPDM. Impact strength of the blends was affected by mixing sequences of the components. The Blends prepared by mixing sequences of san/initiator/EPDM show the highest impact strength of the order of 45 J/m.