A program to determine if non-metallic materials such as polymers, concrete polymer composites, and refractory cements can be utilized as materials of construction in geothermal processes is in progress. To date, several high temperature polymer concrete systems have been formulated, laboratory and field tests performed in brine, flashing brine, and steam at temperatures up to 260°C (500°F), and economic studies started. Laboratory data for exposure times> 2 years are available. Test results indicate that polymer concrete (PC) containing mixtures of styrene--acrylonitrile--acrylamide or methacrylamide produces composites with the best high temperature and chemical resistance obtained to date. The results show that the use of a 12 wt % concentration of a 55 wt % styrene--35 wt % acrylonitrile--5 wt % acrylamide--5 wt % trimethylolpropane trimethacrylate monomer mixture in conjunction with 88 wt % of a 70 wt % silica sand--30 wt % Portland cement aggregate produces a composite with a compressive strength at 20°C (68°F) in the range 25,000 to 30,000 psi. The PC is thermally stable to approximately 240°C (464°F). Results are also available from field exposures of up to 24 months in four geothermal environments. Good durability is indicated. Work at four of these sites is continuing, and plans to initiate tests at other sites are being implemented.