Radiation crosslinking of polymer blends containing the ethylene–propylene terpolymer (EPDM) and polypropylene (PP) was studied. Four binary systems with mixing ratios of 80/20, 60/40, 40/60, and 20/80 w/w and the individual components were γ‐processed. The development of the gel content formed in irradiated blends proved that the increase in PP concentration generated an increasing insoluble fraction. A linear dependence of the gel fraction on PP concentration was found. The optimal dose range for the efficient crosslinking of all EPDM/PP blends was 40–180 kGy. The use of PP customer waste was also examined. The thermal stability of the studied mixtures was assessed in order to state the contribution of the components to the radiation compatibilization of investigated polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 982–987, 2000