This review of the extant research literature focuses on research about content-based language instruction (CBI) programmes in K-12 foreign/second language education in the USA. The review emphasises studies on one-way language immersion (OWI) and two-way language immersion (TWI) programmes, which are school-based and subject matter-driven. OWI primarily targets majority-language students and TWI a combined student population of minority- and majority-language learners. Reference to the few studies on non-immersion CBI programmes in the USA is also included. This article presents a review of the research in relationship to four broad themes: student outcomes, classroom language use and development, the hidden curriculum, and teacher preparation and practice. The research review is followed by a discussion of the research methodologies and theoretical frameworks used in these studies and concluding sections that set suggestions for paths for future inquiry in four areas: student diversity, the role of English in classrooms, teacher development, and achievement research.