Japan has a long tradition of teaching English as a foreign language (EFL). A common feature of EFL courses is reliance on specific textbooks as a basis for graded teaching, and periods in Japanese EFL history are marked by the introduction of different textbook series. These sets of textbooks share the common goal of taking students from beginners through to "able" English language users, so one would expect to find common characteristics across such series. As part of an on-going research programme in which Japanese EFL textbooks from different historical periods are compared and contrasted, the authors have recently focussed their efforts on using textual analysis tools to highlight distinctive characteristics of such textbooks. This article introduces one such analysis tool and describes some of the results from its application to three textbook series from distinct periods in Japanese EFL history. In so doing, the authors aim to encourage the use of textual analysis and seek to expose salient features of EFL texts that would likely remain hidden without such analytical techniques.(Contains 10 tables, 11 figures, and 3 endnotes.)