This editorial introduces the special issue of Evaluation and Program Planning. This issue focuses on four major studies under the treatment improvement protocols (TIPs) evaluation project sponsored by the Center for Substance Abuse Treatment. The goal of these evaluation studies was to gain a better understanding of the effectiveness of TIPs in influencing attitudes and behaviors, the people who are most effective in transmitting new practice guidelines, the barriers to implementation, and the methods that would best transfer information into action. In addition to providing an overview of each article, this introduction addresses the value of using a theory-driven approach to dissemination research. Published by Elsevier Science Ltd.