Response to student writing has been a research concern for composition specialists for the past several decades. However, most research to date has utilized student opinions or researcher judgments about teacher feedback, with researchers rarely consulting teachers themselves as informants. Also, first language (L1) and second language (L2) response research has been completed and disseminated in separate arenas, with little consideration given to the current blurring of boundaries in many educational contexts between L1 and L2 student writers. In the study described in this article, college writing instructors in both mainstream and specialized L2 writing contexts were surveyed (N 5 129) and interviewed (N 5 23) about their backgrounds (training and experience) and their philosophies and practices with regard to response. In addition, samples of their commentary on student papers (3-5 papers per interview subject) were collected, discussed with the instructors, and analyzed. Although most instructors were aware of adapting their approach to feedback for L2 writers, the nature of these adjustments varied dramatically across subjects, as did their overall attitude toward the endeavor of responding to L2 writers. The article concludes with a discussion of practical implications of the findings for teacher response practices and for professional preparation of L1 writing instructors who work with L2 students.