The data release for the geologic map of the Butte 1 degree x 2 degrees quadrangle, Montana, is a Geologic Map Schema (GeMS)-compliant version that updates the GIS files for the geologic map published in Montana Bureau of Mines and Geology Open File Report MBMG 363 (Lewis, 1998). The updated digital data present the attribute tables and geospatial features (points, lines and polygons) in the format that meets GeMS requirements. This data release presents the geologic map as shown on the plates and captured in geospatial data for the published map. Minor errors, such as mistakes in line decoration or differences between the digital data and the map image, are corrected in this version. The database represents the geology for the 4.4 million acre, geologically complex Butte 1 x 2 degrees quadrangle, at a publication scale of 1:250,000. The map covers parts of Deer Lodge, Granite, Jefferson, Lewis and Clark, Missoula, Powell, Ravalli, and Silver Bow Counties. These GIS data supersede those in the interpretive report: Lewis, R.S., 1998, Geologic map of the Butte 1 x 2 quadrangle, southwestern Montana: Montana Bureau of Mines and Geology Open-File Report 363, 16 p., 1 sheet, scale 1:250,000, http://www.mbmg.mtech.edu/mbmgcat/public/ListCitation.asp?pub_id=11212&.