The process approach to writing instruction emphasizes a cycle of revision during which students draft, edit, revise, and redraft their work. In this approach, feedback from teachers or peers and the opportunity to revise written work based on this feedback are considered to be keys to students' development as writers, and the role of instruction in novice learning and appropriation of writing has become a focal concern. Teachers are to treat "the emerging text as an improvable object", with students learning to translate their readers' responses to early drafts of their work into improvement. Despite the acknowledged importance of student-teacher interaction in the development of writing skills, and the investment in resources for implementing writing process policies in districts and schools, relatively few studies have investigated the nature of teachers' comments to students or student uptake of those comments. In this study, the authors investigated the implementation of the process approach to writing instruction in 11 urban middle school classrooms in five schools. They focused on one critical element of the writing process--teachers' written feedback on early drafts of student writings. From a process perspective, writing development involves three key processes: (1) planning; (2) transforming ideas into language and its orthographic representation; and (3) rewriting text to improve it. The authors focused on the students' opportunities to revise and improve writings by investigating the quality of teacher feedback to students on their early drafts, and improvements over subsequent drafts of students' written work. While both the social and written contexts in which feedback is given are important to study, the authors focused on the nature of written instructor responses to student writings. (Contains 6 tables.)