Background: The poor depend on the private sector for much of their primary ambulatory care in middle and low income countries, but quality is variable. Mechanisms that influence the market could be powerful, with large opportunity for leveraging change. We set out to explore potential strategies to improve the quality of health care provided in this sector, with a focus on influencing market mechanisms. Paradoxically, this topic is important to enhancing equity of access to quality health services. Objectives: To a) systematically summarize evidence comparing the quality of private versus public ambulatory care in middle and low income countries; b) evaluate research evidence on strategies to improve the quality of care in the private sector; and c) relate the findings to conceptual models of the market in the framework of new institutional economics. Methods: Systematic reviews with different inclusion criteria are being undertaken: a) comparisons of quality between private and public in one region; b) interventions to influence private sector quality. A third narrative review is examining theory around market mechanisms. For the systematic reviews, protocols have been completed and data extraction is ongoing, using EPPI reviewer software. Results: The preliminary results will be presented. Conclusions: The literature may help policy makers consider their options to improve quality, evidence of benefit, and help establish appropriate monitoring indicators to evaluate implementation. We hope areas worthy of further rigorous evaluation will be identified. The approach is a robust adaption of Cochrane methods appropriate to the policy questions in this area of health systems research.