Although the writing-across-the-curriculum movement is nearly 20 years old, information about the deliberate use of writing for learning in the content areas still is relatively scarce. Most instructors in postsecondary social science courses who use writing continue to stress the improvement ofstudents' writing skills while neglecting the power of writing as a teaching and learning tool in a student-centered (collaborative) classroom. Social and cognitive rationales for purposeful writing-for-learning assignments are provided, not only to enhance communication skills but also to change students' knowledge structures through written dialogue and metacognitive questioning. We describe the extensive use of a variation of the traditional affective classroom journal in an introductory human services course and recommend the teaming of a writing instructor with the instructor in the discipline.