This article is a personal view of the application of research on vocabulary to teaching and how there are three different types or categories of relationship between that research and the teaching to which it is applied: first, where the research is not applied or not applied well, second, where it is reasonably well applied, and third, where it is over-applied. For each of these three categories, I look at what I consider to be the most important areas of research and suggest why they fit into that category. The topics covered include planning vocabulary courses, distinguishing high frequency and low frequency words, extensive reading, the deliberate learning of vocabulary, academic vocabulary and vocabulary teaching.