The design and construction of roads with longer service lives is a priority of civil engineers. The selection of appropriate highway materials with respect to climatic and loading conditions may significantly increase the lifespan of pavements. One material receiving interest in the area of improved roadway performance is polymer-modified binder. The complex behavior of polymer-modified binders, particularly over time, is not yet well-understood by engineers. Therefore, an experimental study was performed to determine the effects of four years of storage at room temperatures (23°C) on the dynamic mechanical properties of polymer-modified binders at intermediate and high temperatures. A typical paving grade (AC-20) and three elastomeric modifiers, each at three concentrations were used. Initial tests were performed in 1995 to evaluate the effects of short-term aging as simulated by the Rolling Thin Film Oven Test (RTFOT) procedure. This study encompasses a second phase of testing occurring after the modified binders were stored at ambient room temperature (23°C) for four years. The study found that significant changes affecting the dynamic response of binders occur during long term storage at a temperature of 23°C. These changes are dependent on the type and concentration of modifier and may be beneficial. Additionally, four mathematical models describing the dynamic response of binders were evaluated and found to be variable in their ability to accurately predict response of modified binders. Most of these models are not well suited for prediction of the response of stored binders.