An important question in the field of English language teaching and learning is 'What is the relationship between research and second language (L2) instruction?'. A second question is 'What should the relationship be?'. This keynote speech explores these two questions. The speech provides a general overview of some of the important insights that L2 research can provide to teachers. It shows that instruction can be effective for L2 learning, development, and acquisition; however, not all instruction is equally beneficial, and researchers are still investigating which types of instruction might be better for specific aspects of language or for developing specific types of knowledge. However, one implication of this research for teachers is that a mix of explicit and implicit instruction might be most effective for developing learners who can communicate accurately and fluently with those around them. [Note: The volume number (9) shown on the PDF is incorrect. The correct volume number is 10.]