Research in second language acquisition has shown that adjusting classroom discussions, textbook reading, and written activities to the language proficiencies of second language learners triggers second language acquisition in subject matter classrooms. Second language researchers find that subject matter teachers should systematically teach discipline-specific language, pay attention to the functional use of language in classroom discussions, and use writing as a learning tool to promote language development. Subject matter teachers should also identify the language that students specifically need to know, including the language structures and essential vocabulary that a teaching unit requires, and integrate these topics into daily instruction. The author shows how two high school biology teachers and a high school social studies teacher effectively taught subject matter by integrating language and content. (Contains 2 figures.)