This thesis investigates the research question of how multiple institutional logics are experienced by individual actors at the micro-level of a nested institutional system. This new institutional literature in organisation studies contends that society is made up of multiple institutions which provide institutional logics in the form of beliefs, assumptions and motives (Friedland & Alford, 1991). These institutional logics can be drawn down progressively by organisational fields, organisations and individuals as a basis for interpretation and action. Despite the conceptual importance of the individual actor in this nested system, limited empirical research has been conducted into institutional logics at the micro level. The thesis explores the research question in the context of professional bureaucracies, which are an exemplar organisational form characterised by both administrative and professional logics. Research into a public hospital as a professional bureaucracy, and focusing on nurses as a category of professionals, was conducted using the methodology of phenomenography, an interpretivist approach developed explicitly to explore participant's lived experiences of a phenomenon. The phenomenographic study entailed conducting interviews with emergency nurses about their daily experiences of working with administrative and professional logics in the hospital emergency department. The study identified three qualitatively different conceptions in which administrative and professional logics were experienced by nurses as competing, co-existing or blended. The thesis makes a contribution to the literature on institutional logics by demonstrating that differential consequences for multiple institutional logics at the micro level may arise because individual actors experience these logics through different institutional mechanisms and carriers. Competing logics and co-existing logics may be experienced through regulatory and normative diffusion mechanisms respectively. In contrast, blended logics may be experienced as a translation rather than diffusion process.