This paper examines the experience of developing primary care organizations (PCOs) in New Zealand and England, exploring how far these new institutional forms have been able to 'tip the balance' of their host health system in favour of primary care. The original objectives for establishing PCOs in the two countries are assessed using published research evidence on the impact of PCOs covering: efficiency and cost containment; the development of clinical engagement and leadership; the development of primary care; and the purchasing of secondary and referred services. It is concluded that in both countries, progress has been made in aligning more closely the individual focus of general practice with the population perspective of the wider public health system. The New Zealand approach of using non-governmental PCOs is judged consistent with harnessing the professional culture of general practice towards community-based public health. By contrast, English primary care trusts (PCTs) are at risk of becoming remote from their origins as purchasers in primary care and general practice, unless the re-introduction of practice-level purchasing can provide GPs with new enthusiasm for local planning and service development.