Abstract It has been 30 years since the Declaration of Alma Ata. During that time, primary care has been the central strategy for expanding health services in many low- and middle-income countries. The recent global calls to redouble support for primary care highlighted it as a pathway to reaching the health Millennium Development Goals. In this systematic review we described and assessed the contributions of major primary care initiatives implemented in low- and middle-income countries in the past 30 years to a broad range of health system goals. The scope of the programs reviewed was substantial, with several interventions implemented on a national scale. We found that the majority of primary care programs had multiple components from health service delivery to financing reform to building community demand for health care. Although given this integration and the variable quality of the available research it was difficult to attribute effects to the primary care component alone, we found that primary care-focused health initiatives in low- and middle-income countries have improved access to health care, including among the poor, at reasonably low cost. There is also evidence that primary care programs have reduced child mortality and, in some cases, wealth-based disparities in mortality. Lastly, primary care has proven to be an effective platform for health system strengthening in several countries. Future research should focus on understanding how to optimize the delivery of primary care to improve health and achieve other health system objectives (e.g., responsiveness, efficiency) and to what extent models of care can be exported to different settings.