Competence and competency assessment in nursing are promoted as necessary to ensure the quality of health care services. The dominant discourse in the international nursing community suggests that competence should be assured through some form of competency assessment, however competence is a controversial concept, with many different definitions. There are significant concerns about the validity and reliability of currently available assessment technologies. Rather than continue the debate about definitions and measurement, I take as my research aim the discovery of how what has come to count as competence became settled. The data for this study was drawn from textbooks, journal articles, meeting minutes, government reports, interviews with senior nurse leaders who were active in the development of the ANRAC Competencies and the ANCI Competency Standards 3e and RN preceptors who assess competence, group interviews with Clinical Development Nurses who assess competence, and observations of newly qualified nurses being assessed by Clinical Development Nurses. Newly qualified nurses were chosen as the focus for this study as they are formally assessed as part of Transition to Practice programs offered by health agencies around Australia. The study focuses on the period 1985 to 2005. Theories from the science, technology and social (STS) discipline informed the analysis. I found that rather than existing as a singular definable reality, competence exists in an undecided set of potentials and is momentarily reified in daily nursing practices in the form of competency standards assemblages. Combined, the semiotic (competence) - material (competency standard) assemblages are created by inventive assessors who work allegorically with multiple competences. This is not the work of assessing competence; rather it is the work of producing competence. The findings of this thesis offer new insight into competence and assessment technologies that can inform further research and development into the practices of competence assessment.