The effects of maleic anhydride modified ethylene-propylene-diene rubber (EPDMMA) and maleic anhydride modified ethylene-vinyl acetate (EVAMA) on the compatibilization of nitrile rubber (NBR)/ethylene-propylene-diene rubber (70:30 w/w) blends vulcanized with a sulfur system were investigated. The presence of EPDMMA and EVAMA resulted in improvements of the tensile properties, whereas no substantial change was detected in the degree of crosslinking. The blend systems were also analyzed with scanning electron microscopy and dynamic mechanical thermal analysis. The presence of EVAMA resulted in a blend with a more homogeneous morphology. The compatibilizing effect of this functional copolymer was also detected with dynamic mechanical analysis. A shift of the glass-transition temperature of the NBR phase toward lower values was observed. The presence of EPDMMA and EVAMA also increased the thermal stability, as indicated by an improvement in the retention of the mechanical properties after aging in an air-circulating oven. (C) 2003 Wiley Periodicals, Inc.