The public cost of immigration is a matter of ongoing and sometimes intense political debate in California. One of the least understood issues in the debate is whether many of those who come to the United States return home and, if so, whether they differ from those who remain. Return migration has important ramifications for a number of policy concerns, including the composition of the immigrant population, the use of social services, and the potential for assimilation. To shed light on this issue, the author analyzes data on return migration for a sample of more than 42,000 immigrants from western Mexico – an area that accounts for a large percentage of California’s immigrants.