A suite of representative specimens of two generations of sphalerite, pink dolomite, and calcite from ten mines of the Miami-Picher district of Oklahoma and Kansas has been studied with the visual method of liquid inclusion geothermometry. Results indicate the following ranges of temperatures of mineral formation for all samples studied, uncorrected for pressure: sphalerite I, 120 to 85 degrees C; pink dolomite, 96 to 76 degrees C; sphalerite II, 105 to 83 degrees C; calcite, 68 to 52 degrees C. The overlapping temperature ranges for sphalerite I, pink dolomite, and sphalerite II are apparent rather than real, caused by grouping together all values for these mineral stages. Correction for pressure requires raising these values by amounts estimated to range from 10 to 15 degrees C.Liquid inclusions in minerals from the Miami-Picher district are judged to satisfy the basic assumptions of liquid inclusion geothermometry.A systematic decline in temperature during deposition of sphalerite I, pink dolomite, and sphalerite II is suggested. No systematic variation of inclusion temperatures was shown in calcite crystals studied. The data obtained suggest that mineralization took place from two successive surges of warm ore solutions, each of which cooled as deposition progressed. Higher ranges of inclusion temperatures were found for minerals collected near the Miami Trough graben, lower ranges for those further from this fault zone. On this basis, it is postulated that warm ore solutions may have entered country rocks from the fault zone, cooling as they spread further into the country rocks.Miami-Picher ores are considered of "hydrothermal" origin in the sense that they have apparently developed from warm aqueous solutions.