This paper reports on two different studies on the language awareness of experienced teachers. It raises issues of how knowledge of grammar, particularly at sentence level, can be developed and applied in the classroom. In the first study, teachers undertaking a postgraduate TESOL practicum generally showed a high level of competence in their use of English grammar but limited metalinguistic knowledge and ability to formulate grammar rules. This finding is in contrast to the teachers' expressed beliefs about the importance of this kind of content knowledge and pedagogical content knowledge (Jensen 2007). In the second study, experienced teachers of languages other than English (LOTE), who already used their own well-developed knowledge of sentence-level grammar in their teaching, reported on their experience of and attitudes to the teaching of grammar (Harrington 2005). Together with the researcher, teachers then undertook a professional development activity which aimed not only to sharpen their own language awareness, but to develop strategies for focusing on grammar-'noticing' in an interactive way in secondary LOTE classrooms. In this paper, we argue that there is a need for second and foreign language teachers to develop language awareness and offer an example of how teacher educators might facilitate this.