Asphalt binder was modified by low-density polyethylene (LDPE) and ethyl vinyl acetate (EVA) polymers to investigate the structure-property relationships of polymer-modified asphalt (PMA). The PMA was prepared in a high-shear blender at 160 degrees C. The optimum blending time (OBT) for each polymer was determined following a separate investigation. OBT was influenced by M-w, MWD, and polymer structure. The influence of M-w of LDPE and vinyl acetate (VA) content of EVA on PMAs was studied by rheological tools. Polymer modification improved the rheological properties of base asphalt. EVA-PMAs were found to be less temperature sensitive than LDPE-modified asphalts. LDPE modification increased flow activation energy (E-a) but EVA modification decreased E-a. Both VA content and M-w of LDPE have influenced the storage stability of PMAs. The low-temperature properties of PMAs and short ageing tests were not influenced by polymer type. On the other hand, the high-temperature properties of PMAs were strongly influenced by M-w of LDPE and VA content of EVA. Overall, EVA with low VA content showed the best temperature resistance to high- temperature deformations, the highest upper service temperature as well as the best storage stability.