DNA typing of biological samples facilitates clearing individuals who have been falsely associated with forensic evidence and reducing the number of potential contributors to a few or only one individual. To exploit the full potential of short tandem repeat (STR) loci, the FBI Laboratory sponsored a community-wide scientific effort to select and establish the core STR loci for the national Combined DNA Index System, CODIS. Allele distributions for 12 or 13 CODIS core tetrameric (STR) loci CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, TH01, TPOX, and vWA were determined in 41 population data sets. The major population groups were comprised of African Americans, U.S. Caucasians, Hispanics, Far East Asians, and Native Americans. There was little evidence for departures from Hardy-Weinberg expectations in any of the populations. In conclusion, substantial population data are available for the 13 CODIS STR loci presented here. These data should facilitate estimation of multiple loci profile frequencies for most scenarios in the United States. Tables, references