Effect of substituting small amounts of ENR 50 (0-30 parts) in NBR compounds on cure characteristics and vulcanizates properties in both gum and carbon black/silica filled systems were investigated. A silane modified NBR/silica system was also studied for comparison. Cure characteristics and vulcanizate properties of both gum and filled systems were improved with the incorporation of 15 parts of ENR 50. Substantial reduction in cure time was observed for both the systems studied. Tensile strength, modulus and tear strength improved, while oil resistance of the blend remained unchanged. Mechanical properties of NBR/ENR/Silica vulcanizates were comparable to that of silane modified NBR/silica system, indicating that ENR act as a reinforcement modifier. Ageing properties of NBR are not adversely affected by the incorporation of 15 parts of ENR 50.