The tensile moduli of polystyrene/polybutadiene blends were studied with reference to the effect of the blend ratio. A comparison between the experimental results and the theoretical predictions of the tensile properties was also made. The models selected were the parallel, series, Halpin-Tsai, Takayanagi, Kerner, and Kunori models. Various theoretical models were applied to predict the location of the phase inversion region in these blends. Different equations were also applied for the prediction of the tensile modulus of cocontinuous structures for comparison.