The objectives of this study were to characterize the effects of the space environment on the compressive behavior of T300/934 graphite/epoxy composite material and on the tensile properties of the neat (unfilled) epoxy matrix material. Both materials were tested in the baseline state and after exposure to electron radiation (total dose of 10,000 Mrads of 1 MeVelectrons at a dose rate of 50 Mrads/hr). Irradiation was conducted under vacuum and simulates 30 year, "worst case", exposure in geosynchronous earth orbit. A compressive test method was developed to characterize thin (8-ply) unidirectional coupons. Compression tests were conducted at cryogenic (-250°F; -157°C), room, and elevated (250°F; 121°C) temperatures. Elastic and strength properties were obtained in the principal material directions (E₁, E₂, v₁₂, v₂₁, X_c, Y_c). Tensile specimens of the neat Fiberite 934 epoxy resin were fabricated and tests were conducted at room and elevated (250°F; 121°C) temperatures. Elastic and strength properties (E, ν, δ_ult) were obtained. Irradiation and temperature were found to have a significant effect on composite and neat resin properties. Properties tended to improve at cryogenic temperature and degrade at elevated temperature. Irradiation degraded properties at all temperatures, with the degradation being most severe at elevated temperature. / M.S.