Contains both raw and processed seismic data recorded during the period 1975-1978 by several geophysical service companies under contract to the USGS for the Powder River Basin of Montana and Wyoming. Four multichannel Vibroseis seismic lines, six Vertical Seismic Profiles, and associated support material (observer's notes, X-Y coordinates, elevations of source and receivers, etc.) are included. The raw (unprocessed) field data and a processed version (reprocessed by USGS in 1995) are contained in standard SEG-Y format files; support material are in ASCII format text files.