In the present article, the effect of ?-ray irradiation of doses 14.85, 30, and 45 kGy on the thermomechanical and tensile properties of blends of cis-polyisoprene and trans-polyisoprene have been investigated. The results on thermomechanical properties show that glass transition temperature increases and height of tan d of material decreases with increasing radiation dose. Tensile measurements reveal that all the tensile properties like tensile strength, Young's modulus, and toughness also show an increasing trend with increasing dose of radiation. This increasing behavior of both thermomechanical and tensile properties has been explained through crystallinity and crosslink density induced by radiation. POLYM. ENG. SCI. 2013. (c) 2012 Society of Plastics Engineers