Professional relationships between doctors and nurses have often been seen as problematic, a barrier to effective collaborative practice, yet little is known about the intrinsic nature of such relationships in the primary care context. This study set out to explore roles of, and relationships between, nurses and doctors currently working in New Zealand primary care settings. Using a qualitative methodology, data were collected using in-depth interviews with 18 individual nurses and doctors working in primary care settings in Wellington, New Zealand. Doctors' and nurses' perceptions of their own and each others' roles, and the perceived relationships between individuals from both disciplinary groups were explored, using principles of naturalistic enquiry in a mixed method of analysis. The study findings indicate that effective interprofessional relationships between individual doctors and nurses can, and often do, exist in New Zealand primary care settings, although they are not universal. The identification and separation of vocational and business roles, and the development of professional identity, form the basis for a theory of trust development in nurse-doctor interprofessional relationships in New Zealand primary care. Professional identity is related to demonstration of professional competence, in turn related to development of mutual interprofessional respect and enduring interprofessional trust.