We prsent here a method for superposing creep measurements on polymer concrete (PC), taken at different temperatures, imposed stresses, and resin contents, onto master curves, which describe the respective responses of various PC systems and their resin binders, to compressive, tensile, and flexural loads. This treatment is extended to systems reinforced with chopped glass fiber and montmorillonite (MMT). The general applicability of this superpasition is tested with creep measurements by other investigators under tensile, compressive, and flexural loads. The results make it possible to predict the long-term creep behavior of unfilled as well as reinforced glassy polymer systems at different temperatures and load conditions from limited, short-term data. Success of the multiple superposition suggests a generalized constitutive equation, which describes the creep compliance of these systems as a product of separable functions of each parameter in the form of shift factors for temperature ( a T ) , stress (ao), resin content (a"), fiber reinforcement (aF), and MMT reinforcement (aM): J(PC) = J r a T ~o ~o ~F ~M t m , where J,. is an appropriately chosen reference creep compliance. The time exponent m does not depend on the chemical nature of the polymer matrix.