This qualitative and inductive doctoral research makes a contribution to public policy sciences by analysing different aspects of the process pertaining to the implementation of a specific public policy in the Belgian health sector: the “Integrated Care for Better Health” plan (IC4BH), launched on 19 October 2015 with the intention of integrating care with regard to chronic patients in Belgium. Based on an ethnographic approach, this research draws on several data collection methods: interviews (N=24), focus groups (N=7), direct observation (N=97 — corresponding to 213 hours of observation), documentary analysis (operational documents) and a multifocused literature review. This manuscript is comprised of seven different chapters. The first chapter is dedicated to methodological aspects, while the next four chapters each correspond to a specific paper (published or as yet unpublished) summarized in an abstract at the beginning of each of those chapters. Each paper deals with a precise research question in order to study different dimensions pertaining to the implementation of the IC4BH plan. The first paper (Chapter 2) addresses the question of how the particular Belgian federal configuration may have had an influence on the implementation of this public policy in the health care sector in Belgium, and, more specifically, on the implementation gap that is apparent when comparing expected and real outcomes in terms of the IC4BH plan implementation. The second paper (Chapter 3) focuses on the pilot project phenomenon, regarded as an object for research, trying to understand how the use of multidisciplinary pilot projects as implementation instruments contributed to reshaping the modes of public governance in the Belgian health sector, in a context of transition and ongoing devolution. The third paper (Chapter 4) tackles the issue of knowing how the use of pilot projects as implementation instruments structured horizontal collaboration between the parties involved in a pilot project. It would seem that the use of ...