The western phosphate field produced about 15 percent, in 1970, of the nation's domestically consumed phosphate rock and contains an estimated 58 percent of the nation's indicated phosphate reserves. The central portion of the western phosphate field, which contains the Dry Valley area of southeastern Idaho, encompasses the greatest amount of mineable phosphate reserves in the smallest geographic area within the western field. Exploration of properties in the area should follow an orderly sequence of literature search, area reconnaissance, detailed target appraisal, and detailed three-dimensional sampling to effectively evaluate each property. Present exploration techniques include topographic analysis, vegetative investigation, profile drilling patterns using a portable rotary-table drilling rig, geophysical logging of the drill holes including gamma-radiation logs, neutron logs, temperature gradient and differential temperature logs, and bulk density logs, trenching, tunneling, and test mining. The economic analysis of exploration programs embodies bookkeeping, project cost forecasting and an economic analysis of alternate methods of exploration. The evaluation of individual phosphate properties includes such variables as geology, mining characteristics, alternate concepts in reserve calculation, transportation and governmental policies. The structural geology of the Dry Valley area is less complex than the structural geology of other phosphate deposits in the western phosphate field. Yet most structural features outlined by drilling in Dry Valley occur elsewhere in the western phosphate field. The stratigraphy of the Phosphoria Formation and its Meade Peak Phosphatic Shale Member is simple and correlatable throughout southeastern Idaho through the use of gamma-radiation logs. The history of land acquisition and property evaluation by FMC in Dry Valley covers a relatively short eight-year period. Future plans for companies operating in the western phosphate field include trading and selling of properties to build mineable units covering large volumes of the estimated 300,000,000 tons of economically surface extractable ore in the Dry Valley vicinity.