Polyurethe grouting has been successfully applied to a lost circulation zone in a geothermal well at Rye Patch, NV. Previously, this zone had resulted in the temporary abandonment of the well after conventional cement plugs had been unsuccessful. The techniques applied to grouting with polyurethane were adapted from civil engineering technology where polyurethane is becoming the grout of choice for sealing boreholes with large voids and high cross flows.