Latino children constitute a large and growing segment of the U.S. population. By 2060, it is estimated that they will comprise one-third (32%) of the three-to-four-year-old population. More than four million children enrolled in preschool programs in the United States are dual language learners (DLLs), and more than 75% of Latina/o children over the age of five enter U.S. schools speaking Spanish. It is critically important that early childhood education (ECE) program administrators and teachers are prepared to work with culturally and linguistically diverse children and their families. This Issue Brief discusses the research on dual language development and makes recommendations for ECE programs and policymakers. [For a related report, "Latina Teachers and the 'BA Challenge': Impacts and Conditions of Increasing Degree Requirements in Early Childhood Education," see ED604027.]