A mineral-resource survey has been conducted for the Caballo and Polvadera Roadless Areas, Los Alamos and Rio Arriba Counties, New Mexico. The rocks in the study areas are chiefly volcanic with minor volcaniclastic sedimentary rocks. There is little promise for the occurrence of mineral or fossil fuel resources in the areas. There has been no mining activity within the roadless areas and chemical analyses of stream-sediment samples show no significant anomalous concentrations of metals. There has been some interest in geothermal resources near the Polvadera Roadless Area and a KGRA (Known Geothermal Resource Area) extends into the southwestern corner of the area. This area has been classified as having probable geothermal-resource potential.