Despite the emphasis placed during the last two decades on public delivery of comprehensive and equitable primary care (PC) to developing country populations, coverage remains far from universal and the quality often poor. Users frequently patronise private providers, ranging from informal drug sellers to trained professionals. Interest is increasing internationally in the potential for making better use of private providers, including contractual approaches. The research aim was to examine the performance of different models of PC provision, in order to identify their strengths and weaknesses from the perspective of a government wishing to develop an overall strategy for improving PC provision. Models evaluated were: (a) South African general practitioners (district surgeons) providing services under public contracts; (b) clinics provided in Lesotho under a sub-contract between a construction company and a South African health care company; (c) GP services provided through an Independent Practitioner Association to low income insured workers and families; (d) a private clinic chain serving low income insured and uninsured workers and their families; and (e) for comparative purposes, South African public clinics. Performance was analysed in terms of provider cost and quality (of infrastructure, treatment practices, acceptability to patients and communities), allowing for differences in services and case-mix. The diversity of the arrangements made direct comparisons difficult, however, clear differences were identified between the models and conclusions drawn on their relative performance and the influences upon performance. The study findings demonstrate that contextual features strongly influence provider performance, and that a crude public/private comparison is not helpful. Key issues in contract design likely to influence performance are highlighted. Finally, the study argues that there is a need before contracting out service provision to consider how the performance of private providers might change when the context within which they are working changes with the introduction of a contract.