Learner diaries, or dialogue journals, are popular in second language teaching. Numerous teaching, learning, evaluative, and research-related uses for them have evolved. Pedagogically, they are used to identify and allay anxiety, offer advice on specific difficulties, provide study skill and individual feedback, encourage student self-assessment, encourage curiosity about the target culture and keep personal records of foreign travel, and practice language use. For evaluation, they provide information for short-term adjustment of methods/materials and group dynamics, and for teacher assessment. In research, journals can help investigate language learner behavior, especially outside class, examine student feelings and conceptualizations, and explore how these factors relate to learning. Variables in diary research requiring consideration include journal layout, access, assignment administration, and feedback. Practical difficulties that can arise from these variables include marking or grading of entries, conflicting student and teacher purposes, conflicting teacher and administrative uses, and first- versus second-language use in entries. For diary use in class, teachers should plan their content and confidentiality, anticipate subsequent guidance to students, decide to what extent entries are a required activity, and specify diary uses.