As more and more schools implement professional learning communities (PLCs), school librarians often ask: What is the role of school librarians in PLCs? What should they be doing to contribute? What are their colleagues in other schools doing? In this article the authors explore these questions by first describing eight potential roles for school librarians as members of PLCs: (1) information specialist; (2) staff developer; (3) teacher and collaborator; (4) critical friend; (5) leader; (6) researcher; (7) learner; and (8) student advocate. Then they report the findings of a research study conducted by one of the authors; the study examined what school librarians are actually doing in PLCs, as well as the barriers that prevent their full participation. The goal is to help school librarians make the most of PLCs. (Contains 2 tables.)