Experiments have been conducted to determine the feasibility and techniques for impregnation and in situ polymerization of liquid monomers in preformed concrete, and the inclusion of monomers directly into the fresh concrete mix, followed by polymerization. Polymerization by both gamma radiation and chemical reaction in the presence of heat is being studied. Studies include monomer screening tests, development of process technology, and development of applications. It appears that the cost of the treatment will be reasonable. Concrete test specimens are prepared and evaluated at the Bureau of Reclamation. Brookhaven National Laboratory performs the impregnation and polymerization. All monomers evaluated to date produce improved properties, their effects in concrete varying only in degree. Improvements in properties resulting from the impregnation of concrete with methyl methacrylate followed by irradiation include the following: Compressive and tensile strength and modulus of rupture have been increased from between 256% to 290%; water permeability has been decreased to negligible values; water absorption has been decreased by as much as 95%; and resistance to abrasion, cavitation, freeze-thaw attack, and to distilled water, soluble sulfates, and acid corrosion has shown significant improvements. For high-temperature desalting plant applications, monomers which have high-temperature stability were selected for screening tests. Compressive and tensile strengths and elastic properties measurements performed to date on four monomer systems at temperatures up to 290°F indicate that 60% styrene plus 40% TMPTMA produces the best strength properties, followed by 90% diallyl phthalate plus 10% methyl methacrylate. Future tests of polymer concrete for desalination plant applications include structural and physical properties measurements following varying periods of exposure to circulating synthetic sea water brine at temperatures up to 290°F.