This research aims to improve health care for New Zealanders through studying the four regional District Health Board (DHB) groupings which together cover all of New Zealand (NZ). The four regional DHB groupings are fundamental to delivering better integration of health care as they plan, fund and deliver health services in their defined geographical regions, with the aim of reducing fragmentation, duplication and service vulnerability. We do not know if these four regional DHB groupings have delivered improved health outcomes for New Zealanders and whether, if they have achieved this, what organisational features explain this success. This research will use a combination of interviews with key stakeholders and analysis of routinely collected health system measures to answer these questions. It seeks to explore if regional DHB groupings can improve health outcomes and, if so, to understand what it is about the way they operate that may explain their success.