The Census Bureau published final criteria for both census tracts and block groups in the Friday, March 14, 2008 Federal Register. The notices, "Census Tract Program for the 2010 Decennial Census--Final Criteria" and "Census Block Group Program for the 2010 Decennial Census--Final Criteria," are available on the Federal Register's website at the following links: Census Tract Final Criteria: < http://a257.g.akamaitech.net/7/257/2422/01jan20081800/edocket.access.gpo.go… Block Group Final Criteria: < http://a257.g.akamaitech.net/7/257/2422/01jan20081800/edocket.access.gpo.go… Both notices also will be available via the Census Bureau's Participant Statistical Areas Program page at: < http://www.census.gov/geo/www/psap2010/psap2010_main.html The block group notice announces the Census Bureau's decision that the minimum population threshold for block groups will continue to be 600 persons. Questions and requests for further information should be addressed to the Geographic Standards and Criteria Branch, Geography Division, Census Bureau via e-mail at &lt;geo.psap.list(a)census.gov&gt; or telephone at 301-763-3056. ______________________________________ Michael R. Ratcliffe Chief, Geographic Standards and Criteria Branch Geography Division U.S. Census Bureau 4600 Silver Hill Road/ MS-7400 Washington, DC 20233-7400 301-763-8977 michael.r.ratcliffe(a)census.gov