An expatriate second language teacher working in Japan describes and discusses his use of a reflective dialogue journal, written with a colleague using electronic mail (e-mail) and using a collaborative approach to professional development. Four topic areas discussed in the collaborative journal are examined: features of doing cooperative development be e-mail; new teaching ideas and items for future research; clarification of beliefs about teaching and learning; and identification of specific instructional trends and concerns. Each of these areas is explored, using excerpts from journal entries as illustration. It is concluded that the collaborative journal can be a useful tool for teachers' professional development, affording opportunities for reflection and integration not always available in oral interaction, yet facilitating dialogue between colleagues. Contains 28 references. (MSE)