Morphology and tensile properties of several styrene-butadiene copolymer reinforced asphalts have been investigated. In all cases, the raw materials were commercial samples; for the styrene-butadiene copolymer, a branching (nonlinear) block polymeric chain of high molecular weight was used. On the other hand, the asphalt was a nonoxydized commercial sample. The raw materials were characterized prior to making the composite. The morphology and mechanical properties of composites obtained at different chemical compositions were determined, and a comparison of these experimental results to different models, according to the composite morphology, is shown.