Introduction: Positioning Liaison Librarians for the 21st Century Karla Hahn, Assistant Executive Director, Research, Teaching, and Learning, ARL L iaison positions exist at nearly every research library, and a recent ARL member survey documented a substantial broadening of liaison roles1. Many believe that liaison librarian functions are becoming more central to fulfilling the library’s mission in a digital age. While research libraries may agree on the importance of the position, how to reconfigure liaison work has become a topic of broad concern. Identifying emerging roles and determining how to develop corresponding liaison capabilities are common challenges. The articles in this special issue highlight several new roles that are being fostered in research libraries and offer different leadership perspectives on the change process. Two authors are associate university librarians with broad responsibilities for managing the development of new functions and responsi- bilities of their institutions’ public services staff (Williams and Dupuis). Two are programmatic experts leading the development and delivery of services that require liaison support for effective engagement with faculty clients–scholarly communication (Kirchner) and data management (Gabridge). Our fifth author is a liaison librarian with a personal commitment to reinvention (Whatley) describing the change process from the inside. Amidst the diversity of stories and assessments gathered here, several recurrent themes stand out. New forms of relationship building, particularly with faculty, are central to effective liaison functions. New kinds of relationships are needed to respond to the changing work of faculty and researchers and to constantly evolving learning outcomes, research processes, and communication practices. In addition, research libraries are increasingly seeking to influence RLI 265 1 AUGUST 2009 RESEARCH LIBRARY ISSUES: A BIMONTHLY REPORT FROM ARL, CNI, AND SPARC