Background: Physicians, health care organizations, governments and communities are increasingly interested in how trust is built throughout the health system. Current science on building trust draws on diverse literature from business and consumer science to healthcare, and theory development has predominately focused on factor based models. We propose a process based theoretical model for trust building which may better reflect the complex and dynamic nature of trust itself. In doing so, we propose a new measurable dimension of the trust building process: reciprocity cycles. Cooperative reciprocal relationships are its building blocks, enabling stakeholders to “try out” their interactions with less risk, and to calibrate their level of effort, time and emotional investment. Reciprocity cycles includes three measurable elements: common goals, self-interests and gratitude/indebtedness.Methods: We applied the model, developing outcomes and measures in close-to-community health partnerships in Kenya. A 3-day workshop designed to stimulate problem solving and collaborative teamwork using human centered design principles was offered in 2 community health units in diverse contexts (rural agrarian and peri-urban flower farm slum), each with about 30 community health volunteers (CHVs) serving a population of approximately 5,000. Each unit formed separate teams representing specific villages; we followed these 9 teams between 18 to 24 months.Results: All 9 volunteer CHV teams delivered on self-directed public health outcomes across the spectrum of social determinants of health over the follow up period, with no funding, only using their own locally available resources. Projects were diverse, including immunization, composting toilets, hygiene, neonatal and reproductive health and public gardening. All 9 teams demonstrated trust building reciprocity cycles with articulation of common goal, self-interest, and gratitude/indebtedness. Conclusion: A process model of trust building, defined by reciprocity cycles, can be stimulated with a short intervention (illustrated here in close-to-community health systems) resulting in trusting relationships that drive agency and co-production of positive outcomes for health systems. In addition, it offers a simpler, more useful framework for trust building and measurement than traditional models of trust in health systems research. Early findings illustrate reciprocity cycles are scalable and adaptable, with potential utility at multiple levels of health systems.