Primary health care (PHC) reforms focus on improving access to and effectiveness of general practice services, with greater emphasis on health promotion, prevention and chronic disease management, and integration with population health approaches. Currently, reforms are often based on scant evidence from the most accessible and easily known PHC domains and activities, yet most PHC is complex and poorly understood. Complexity theory is based on understanding patterns that are not predictable by traditional evidence and social knowledge, within a complex adaptive system. Complexity knowledge provides a way of understanding the general practitioner's role in PHC in self-organising local networks, with a capacity to generate new solutions integrated through historical and social connections. Complex systems provide a framework for an expanded knowledge base, debate and discussion of reforms and development of PHC goals and strategies.