In Victoria the primary health care sector is in a period of change intended to strengthen the integration of a complex service system through a process of partnership development based on collaboration. The partnerships are voluntary alliances of the primary care service providers, usually within a locality of two to three local government areas. Their purpose is to improve the health and wellbeing of the local population by strengthening inter-agency coordination in the areas of needs identification, planning and service delivery. Trust is a key issue in this process. This paper is a report of the first stage of a study to explore trust in the context of relationships between organisations in the primary care sector.