Migration data can be divided into two broad types: “stock” or census and survey data and “flow” or administrative data. Both stock and flow data are valuable resources for analyzing the migration process. In the statistical system of the United States, the U.S. Census Bureau is the primary source for census and survey data on the foreign born. The Department of Homeland Security and the U.S. State Department provide several different administrative sources for studying immigration. The goal of this study is to review the best sources of government data available for analyzing (1) the size, distribution, and characteristics of the foreign-born population and their households and (2) the level of immigration into the United States, and the distribution and characteristics of immigrants by status.