This monograph provides a comprehensive description and analysis of the literacy proficiencies of the adult immigrant population (16-65 years old) in the U.S. in recent years and assesses their implications for the labor force behavior, employment, earnings, incomes, and civic behavior of the immigrant population. The first section will present a brief overview of the unprecedented increase in the nation's immigrant population over the past decade and its impact on the growth of the nation's resident population and civilian labor force. Some of the educational and English speaking deficits of these new immigrants will be briefly reviewed. The second section will describe and assess the literacy performance of the nation's immigrant population on each of the four literacy scales, compare their performance to that of the nation's native-born population, and review variations in the literacy performance of the immigrant population across educational subgroups, years spent studying English, and length of stay in the U.S. The third section will compare the literacy proficiencies of immigrants in the U.S. with those of their counterparts in 19 other high-income countries across the world and identify the percentile rankings of the test scores of the U.S. immigrant population along the literacy skills distribution for all adults in 20 high-income countries around the world.