Current recommendations for achieving high-quality professional development for teachers include the creation of a professional learning community. Key to the success of this approach, however, is the role of the peer mentor or coach. This study examined the experiences and perceptions of 31 professional development coaches in order to highlight the characteristics believed to be essential for success. Results suggest that, while content expertise is perceived to be important, coaches believe that strong interpersonal skills are more critical since, without them, they are unable to use their content knowledge to facilitate changes in teachers' practice. Suggestions for selecting and training peer coaches are included.