Immigrant youth who do not attend schools in the United States fare poorly on many standard measures of well-being, such as educational attainment, English language ability, earnings, health insurance coverage, and poverty status. Most federal and state dollars spent on youth do not reach these young people because the dollars go through educational institutions they do not attend. If policymakers wish to improve the well-being of this very vulnerable young immigrant population, traditional school systems are not likely to be a place to reach them. A federal program, the Migrant Education program (MEP), aims to serve out-of-school immigrant youth as a part of its mission, as do a few local and state programs. This report describes the population of out-of-school immigrant youth in California and the subset of this group served by MEP. The report uses census data to describe this population and then turns to program data from two regions in California's Migrant Education Program. these data not only help us understand educational backgrounds, socioeconomic needs, and academic goals more thoroughly than do the census data, but they also help us understand how the populations in the two regions may differ. Analyses of these data also lead us to suggest some changes to MEP for out-of-school immigrant youth, such as ways to target services, improve future data collection, and enhance program organization.