During 1993 and 1994, the BOReal Ecosystem-Atmosphere Study (BOREAS) Trace Gas and Biogeochemistry team #12 (TGB-12) collected several data sets to support their analysis of soil carbon content in the Northern Study Area (NSA). The primary data set (BOREAS TGB-12 Soil Carbon Data over the NSA) is described in some detail. Other ancillary information was stored and provided in two sets of soil pit description and surface vegetation transect files. In addition, a site description file provides more information on the positioning of the sampling sites. These files contain additional information that complements the data contained in the primary data set.