The results of experimental and theoretical investigation of epoxy EDT-10/glass-bead plastics at long-term (10 years) exposure in water are presented. The curves of water absorption and swelling are determined. It was expected that the addition of hollow glass spheres (beads) must substantially reduce the sorptional capacity of a material, because of reduction of the volume content of the matrix, and therefore, because of reduction of the volume where the molecules of water can diffuse. However, the water absorption process in glass-bead filled plastics was found to continue during the total term of the experiments without a tendency to stop. After ten years the equilibrium state was not achieved and the concentration of water in the composite specimens became more than the equilibrium concentration of water in unfilled EDT-10 epoxy. The swelling coefficient was found to be a non-linear function of water content. It was found that the initial parts of experimental curves of water absorption and smelling (during the first year of exposure) show an agreement with calculated data, good enough for engineering applications. Subsequently the discrepancy between the experimental results and calculated data increased. The possible reasons for such a discrepancy are discussed.