Objective: To describe events leading to development of a professionwide consensus definition of medication therapy management (MTM) and attendant programs and services and present the document (definition, services, and program requirements) resulting from the process. Data Sources: Author's own knowledge and records of events. Summary: Following the late 2003 passage of the Medicare Prescription Drug Improvement and Modernization Act, the pharmacy profession had a need to act quickly to define MTM so that a consensus definition would be available as regulations implementing the Medicare Part D benefit were being written. The American Pharmacists Association facilitated this process by convening a broad working group of members and other involved parties to draft a preliminary definition. The Pharmacy Practice Activity Classification was used to check elements of the definition for consistency with services being offered in a wide variety of settings. A professionwide stakeholders conference was then convened with representatives from each of 11 national pharmacy organizations. This group, following a daylong meeting in late May 2004 and several weeks of e-mail messages and conference calls, finalized the MTM definition, which was then approved by the chief executive officers of all 11 groups. Conclusion: Through the extraordinary efforts of the numerous organizations and participants, the MTM Services Definition is one that is applicable within diverse pharmacy practice segments, whose services are feasible for a majority of practitioners to implement, and whose elements are supported by a profession-wide consortium of 11 national professional pharmacy organizations. This historic achievement is the first step on a journey to find the best ways to effectively deliver MTM services to patients.