There is a growing awareness of the importance of academic vocabulary, and more generally, of academic language proficiency, for students' success in school. There is also a growing body of research on the nature of the demands that academic language places on readers and writers, and on interventions to help students meet these demands. In this review, we discuss the role of academic vocabulary within academic language, examine recent research on instruction in academic vocabulary, considering both general academic words and discipline-specific words, and offer our perspective on the current state of this research and recommendations on how to continue inquiry and to improve practice in this area. We use the metaphor of "words as tools" to reflect our understanding that instruction in academic vocabulary must approach words as means for communicating and thinking about disciplinary content, and must therefore provide students with opportunities to use the instructed words for these purposes as they are learning them. (Contains 1 table.)