This chapter begins by justifying the need to conduct research on TESOL materials and textbooks. It then presents three different approaches to materials research focusing on content (examining materials and textbooks at the level of the page), consumption (studying how learners and teachers make use of materials), and production (investigating how materials and textbooks are written and published), explaining and exemplifying each approach by reviewing studies of each type. The chapter ends by describing examples of current innovative materials research, presenting an agenda for future researchers in the field to pursue. Among the research projects proposed is work to investigate how closely teachers adhere to or deviate from their textbook materials, research to determine the effectiveness of teachers' use of materials, and explorations of how in-service teachers' professional development programmes can enhance teachers' competence as materials designers and consumers.