TREX, which stands for "translating into the mother tongue as an exercise in written language," is a classroom technique for exploring the native language by translating from a second or source language. The central feature is the individual student activity of translating, with subsequent group examination and comparison of lexical, syntactic, and stylistic differences. The approach has the advantages of using a familiar language and using the students' own products as the instructional material, but without the potential for embarrassment when totally student-written compositions are used in classroom discussion. Competence in the second language equal to that in the native language is not necessary, and since the content of the translation is predetermined, the student can concentrate on expression. Because the exercise is written, oral language habits are less likely to interfere. Texts should be representative of the native language and culture, authentic and written for native readers, coherent and complete, and without illustrations. Brief texts such as proverbs may be adequate. Teachers can comment on the texts from the native- or second-language perspective, or through linguistic comparisons. Students who would benefit from TREX include immigrants, students in a bilingual community, teacher trainees, especially future native language teachers, and college-bound students. (MSE)