This article analyzes the role that individual differences in children's cognitive, Spanish competence, and socio-emotional and behavioral skills play in predicting the concurrent and longitudinal acquisition of English among a large sample of ethnically diverse, low-income, Hispanic preschool children. Participants assessed at age 4 for language, cognitive, socio-emotional, and behavioral skills were followed through kindergarten. Multivariate analyses demonstrated that Spanish-speaking preschoolers with greater initiative, self-control, and attachment and fewer behavior problems at age 4 were more successful in obtaining English proficiency by the end of kindergarten compared to those initially weaker in these skills, even after controlling for cognitive/language skills and demographic variables. Also, greater facility in Spanish at age 4 predicted the attainment of English proficiency. Social and behavioral skills and proficiency in Spanish are valuable resources for low-income English language learners during their transition to school.Keywords: English language learner (ELL), dual language learner, Latino/Hispanic, social skills, English acquisitionThe number of English language learners (ELLs) in the United States has been increasing progressively in recent years. ELL enrollment in schools more than doubled between 1997 and 2008 (National Clearinghouse for English Language Acquisition, 2010). Hispanic children, who speak Spanish as their first language (L1), make up the largest proportion of ELL students in today's schools (U.S. Census Bureau, 2010). Given that (a) Hispanics are the largest and fastest growing minority group in the United States; (b) disproportionately high numbers of Hispanic children live in poverty (Chau, Thampi, & Wight, 2010); and (c) Hispanic children, as a group, struggle with relatively poor educational achievement, Garcia and Jensen (2009) argued that young Hispanic children constitute an urgent demographic imperative requiring considerable research and policy attention.One of the key questions has to do with the conditions under which, and the speed with which, young Hispanic children acquire English. Depending on the pattern and timing of exposure to and support for both English and Spanish in the early years, there are many possible language outcomes for such children-some become fully bilingual fairly early on in childhood, learning English and maintaining Spanish in the process; some remain predominantly Spanish speakers with only limited English proficiency; and some become fully competent in English at the expense of Spanish. The current article examines child-level predictors of progress toward proficiency in English during pre-K and kindergarten among Spanish-speaking children in poverty. ELL children who become fully proficient in English, and who do so earlier in their educational career, do better later in school than those who continue to struggle with English proficiency (Halle, Hair, Wandner, McNamara, & Chien, 2012). Of course, English proficiency is only one of th...