Two case studies of language use in bilingual classrooms are presented. The first case study focuses on the functions of the teacher's speech in a twelfth grade civics class. One 50-minute lesson was recorded and transcribed. The two classroom languages, English and Spanish, were coded according to their use for information, elicitation, direction, metastatement, expression, humor, followup, and reply. The teacher used English 55 percent of the time. English predominated in the functions of direction and metastatement, two potentially significant areas of imbalance. The language use patterns of children were observed in an intensive study of 12 children selected from two bilingual second grade classrooms. The speech of each child was recorded for an entire day. The amount, complexity, and function of speech in each language were analyzed. It was found that group setting affected language use but that this effect was mediated by teaching style. The small group setting provided the most favorable context for language use. Also, the students rarely used their weaker language for natural communication in the classroom. They did use their weaker language for a variety of communicative purposes, indicating that the bilingual classroom is a promising setting for second language learning. (RW)