This systematic literature review examines previous studies of elementary school immersion programs with special attention to Spanish immersion programs and their effect on the English language development of students who speak English as a first language. The examination of previous research lays the groundwork for a future study in which the English language development of elementary students enrolled in Spanish immersion programs in the Grand Rapids Public Schools will be tested at the beginning and the end of the school year, to measure the effects of receiving dual-language instruction. This future study will be unique in that it will focus on one-way immersion programs rather than the two-way immersion programs commonly studied in other research. The research for this review is compiled from databases available through Grand Valley State University libraries. Some previous studies report that enrollment in Spanish immersion programs enhances various aspects of English language development, such as receptive vocabulary, literacy, and metalinguistic ability; other studies do not show significant English language development benefits.