Feedback is widely seen as crucial for encouraging and consolidating learning, and this significance has also been recognised by those working in the field of second language (L2) writing. Its importance is acknowledged in process-based classrooms, where it forms a key element of the students' growing control over composing skills, and by genre-oriented teachers employing scaffolded learning techniques. In fact, over the past twenty years, changes in writing pedagogy and research have transformed feedback practices, with teacher written comments often supplemented with peer feedback, writing workshops, conferences, and computer-delivered feedback. But while feedback is a central aspect of ESL/EFL writing programs across the world, the research literature has not been unequivocally positive about its role in writing development, and teachers often have a sense that they are not making use of its full potential. In this paper we examine recent research related to feedback on L2 students' writing, focusing on the role of feedback in writing instruction and discussing current issues relating to teacher written and oral feedback, collaborative peer feedback and computer-mediated feedback.