Tensile properties including Young`s modulus and tear strength were measured for four different rubber compounds; natural rubber(NR), styrene-butadiene copolymer(SBR), ethylene-propylene dime monomer(EPDM), and brominated isobutylene-p-methyl-styrene copolymer(BIMS) as a function of temperature and degree of cure. To see the effect of over cure, a measurement was made of the tensile strength and swelling behavior of the over-cured rubber compounds. Young`s modulus, E, was found to have linear dependency on the degree of cure for all rubber compounds. EPDM and BIMS showed the highest and lowest slopes, respectively. The slope of NR and SBR lay between EPDM and BIMS. Tear strength, Gc, decreased in the order of NR$gt;BIMS$gt;SBR$gt;EPDM. As the cure time was extended the degree of cure of NR and SBR decreased, while that of BIMS increased. EPDM showed little change in the degree of cure.