A total of 584 stream-sediment and rock samples were collected from within or near the Ten Mile West Roadless Area, Boise and Elmore Counties, Idaho, as part of a geologic study aimed at appraising the mineral resource potential of the area. Emphasis was placed on stream-sediment samples because stream sediments represent the erosional products of a drainage system and offer a rapid means of locating anomalous concentrations of ore-forming elements. An unusually high proportion of the stream-sediment samples contained concentrations of silver and molybdenum. Unaltered rocks of the area contain normal quantities of the common rock-forming elements. Some exposures of altered or mineralized rocks and some quartz veins contain significant quantities of gold and silver.