In 1978, Primary Health Care (PHC) was formally recognised, in the Declaration of Alma-Ata, as the key to achieving the World Health Organisation's goal of 'Health For All by the Year 2000' (HFA). PHC was seen as the solution to the inadequate illness management systems that had developed throughout the world. It was hoped that PHC would address some of the major inequalities in health observed both within and between countries by its balanced system of treatment and disease prevention. The WHO envisaged that PHC would take place as close as possible to where people live and work and be the first element of a continuing health care process. Additionally, health service collaboration and multi-professional partnerships were expected to replace professional boundaries and competition. Shortly after the Declaration of Alma-Ata, the World Health Organisation, supported by national and international nursing bodies, proposed that nurses would be the driving force behind the HFA movement as active partners in inter-professional teams, leaders in health care and resources to people rather than resources to other health professionals. In the ensuing years, although community health nurses were acknowledged by the government and the nursing profession as key players in PHC in Australia, practice nurses (nurses who are employed in general medical practices) were not identified within this group. Hence, it appeared as though these practice nurses were 'invisible', not considered important to PHC in Australia, or simply overlooked as a major influence on population health. The purpose of this study was to describe the current role of these nurses and to identify and analyse the factors that influenced their scope of practice and hence their contribution to PHC. The research was conducted as a case study of practice nurses in one Division of General Practice in southeast Queensland. The study was influenced by the constructivist paradigm of inquiry and utilised a complementary sequence of quantitative methods followed by qualitative investigation. The first stage of the study comprised a telephone followed by mail survey of general practitioners and practice nurses employed within the Division. This was followed by a second stage, which involved group and individual interviews of key informants and was supported by document review and observation. The study revealed that the practice nurse role is essentially one of assistant to the general practitioner wherein the nurse undertakes basic assessment procedures to aid the medical diagnosis, carries out delegated therapeutic procedures, and contributes to the administrative functioning of the practice. Autonomous nursing initiatives, which appear to be largely opportunistic and incidental to delegated activities, include physical and emotional support of patients, clarification and reinforcement of medical instructions, and the provision of health education. The practice nurse's role, and hence contribution to PHC, was found to be constrained by a number of factors. These factors include the current funding arrangements for general practice, the view that practice nurses are an option rather than a necessity, the general practitioners' control of the practice setting, the appropriation of nursing work to medical receptionists, the lack of professional development opportunities, and the practice nurses' passive acceptance of their circumstances. However, both general practitioners and practice nurses appreciate the value of nursing services in general practice and GPs would sanction the employment of more nurses, if given financial incentives, especially for the purpose of preventive care. The majority of practice nurses believe their role should be expanded to include autonomous functioning while most of the GPs were amenable to some extension of nursing practice but reticent or opposed to any independent interventions. There appears a need in Queensland for courses to prepare practice nurses for advanced practice if they want to expand their role in PHC beyond that of assistants to GPs. It would also seem to be in the nurses' interests to initiate a professional association of practice nurses as a vehicle to explore other issues relevant to their professional development. In addition, if PNs want to expand their role they will need to demonstrate improved patient outcomes and cost effectiveness.