In keeping with the neo-liberal emphasis on privatization, international aid has been increasingly channeled through non-governmental organizations (NGOs) and their expatriate technical experts to support primary health care (PHC) in the developing world. Relationships between international aid workers and their local counterparts have thus become critical aspects of PHC and its effectiveness. However, these important social dynamics of PHC remain understudied by social scientists. Based on three years of participant-observation in Mozambique, this paper presents an ethnographic case study of these relationships in one central province. The Mozambique experience reveals that the deluge of NGOs and their expatriate workers over the last decade has fragmented the local health system, undermined local control of health programs, and contributed to growing local social inequality. Since national health system salaries plummeted over the same period as a result of structural adjustment, health workers became vulnerable to financial favors offered by NGOs seeking to promote their projects in turf struggles with other agencies. It is argued that new aid management strategies, while necessary, will not be sufficient to remedy the fragmentation of the health sector. A new model for collaboration between expatriate aid workers and their local counterparts in the developing world is urgently needed that centers on the building of long-term equitable professional relationships in a sustainable adequately funded public sector. The case study presented here illustrates how the NGO model undermines the establishment of these relationships that are so vital to successful development assistance.