||The nursing profession is entering an exciting time of new professional opportunities. As the United States of America (USA) deals with its health care crisis, nursing is positioned to determine the trajectory of health care and health policy. However, nurses are underrepresented in major forums where they could be change agents on this new path. Nursing must lead the charge to effect change in the delivery of patient care and the health policy debate. This could be accomplished through the nurse's role as advocate for the patient and profession. However, the nurse as advocate is a poorly understood, inadequately researched, and minimally practiced role. Studies have failed to determine the nurse advocate role in its complexities. The aim of this research investigation was to increase the current knowledge about the nurse advocate role, and to discover and explicate substantive theory concerning this role. This investigation used the grounded theory methodology of Corbin and Strauss, including the philosophies of pragmatism and symbolic interactionism, to examine and discover the advocacy process as it informs the role of the nurse advocate. Thirteen peer-identified FAAN nurse leader/advocates were chosen purposively to form a varied and highly experienced study group. These participants were interviewed and their interview transcripts were used as the primary data sources in addition to the researcher's field notes, memos and participants' curriculum vita. Transcripts were coded using open and axial coding techniques that allowed the emergence of a conceptual definition of advocacy, the core phenomenon to advocate and five components and their subconcepts. These analyses led to the theoretical and categorical relationships that were explicated. The product was the Sessler Branden Advocacy Matrix Theory (SBAMT). This study has contributed to the extant knowledge of the nurse as advocate and has explicated the role of the nurse advocate. This theory has bridged the existing knowledge with a substantive, pragmatic theory that can be applied and utilized by any nurse in any situation where advocacy is needed.