Literacy coaching as a means of professional development has great potential for increasing student achievement, teacher effectiveness, and school success. However, schools and districts can inadvertently undermine the potential of coaching when a coach's role is not clearly defined and when the position is not adequately supported and protected. Coaches who serve multiple schools, whose primary function is to enforce program fidelity, or who are not given adequate training in order to support their teachers are in danger of failing in their roles as coaches. In addition, coaches who do not collaborate closely with building level administrators or who are expected to "fix" incompetent teachers cannot hope to transform instructional practice with any level of success. For coaching to be an effective agent of change in schools, district and building administrators should become knowledgeable about the numerous roles in which coaches do, and do not, serve.