This report presents the final data from a 5-yr Bureau of Mines study designed to determine the surface subsidence characteristics resulting from longwall coal mining in a geologic environment common to the western United States. It includes a description of the geologic setting of the study site, the mine plan, measurement techniques, and results of the monitoring program. Measured subsidence values were obtained over four adjacent longwall panels. Major subsidence characteristics such as longitudinal and transverse profiles, angles of draw, time-related subsidence development, and critical width are discussed. The maximum subsidence value of 5.8 Ft was 68 pct of the mining thickness. The average angle of draw was 30 deg. Subsidence at the center of the first panel continued for 46 months following undermining. The lengths of the longwall panels precluded a definitive determination of the critical width and maximum possible subsidence.