Stress-strain curves of some glassy, polymeric materials, i.e. polymethyl methacrylate (PMMA) or polycarbonate (PC), are determined in a very wide range of strain rates under conditions of uniaxial strain. A plate impact testing apparatus, a drop hammer testing machine and a universal testing machine are used for the high strain-rate (10(7) s(-1)), medium strain rate (10(2) s(-1)) and low strain rate (10(4) s(-1)) tests, respectively. The plate impact test is used to obtain stress-strain curves for PMMA and PC undergoing uniaxial strain. Stress-time histories are obtained in PMMA or PC at impact velocities 600 to 700 m/s using polyvinylidene fluoride (PVDF) gauges. Lagrangian analysis is used to extract strain-time histories from the experimental stress data. The drop hammer compression test is used to determine stress-strain curves at medium strain rate under conditions of uniaxial stress by using an extrapolation procedure. For the low strain rates the stress-strain curves are determined under conditions of uniaxial stress by the universal testing machine combined with the extrapolation method. The stress-strain curves at medium and low strain rates in uniaxial strain are constructed on the basis of the Wood's equation from the uniaxial stress data. It is assumed for strains up to roughly 0.1 that PMMA and PC are elastic, perfectly plastic material and Young's moduli of these materials are rate dependent. The effects of strain rate on the stress of PMMA and PC are investigated under conditions of uniaxial strain.