In 1978, at an international conference in Kazakhstan, the World Health Organization (WHO) and the United Nations Children’s Fund put forward a policy proposal entitled “Primary Health Care” (PHC). Adopted by all the World Health Organization member states, the proposal catalyzed ideas and experiences by which governments and people began to change their views about how good health was obtained and sustained. The Declaration of Alma-Ata (as it is known, after the city in which the conference was held) committed member states to take action to achieve the WHO definition of health as “state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” Arguing that good health was not merely the result of biomedical advances, health-services provision, and professional care, the declaration stated that health was a human right, that the inequality of health status among the world’s populations was unacceptable, and that people had a right and duty to become involved in the planning and implementation of their own healthcare. It proposed that this policy be supported through collaboration with other government sectors to ensure that health was recognized as a key to development planning. Under the banner call “Health for All by the Year 2000,” WHO and the United Nations Children’s Fund set out to turn their vision for improving health into practice. They confronted a number of critical challenges. These included defining PHC and translating PHC into practice, developing frameworks to translate equity into action, experiencing both the potential and the limitations of community participation in helping to achieve the WHO definition of health, and seeking the necessary financing to support the transformation of health systems. These challenges were taken up by global, national, and nongovernmental organization programs in efforts to balance the PHC vision with the realities of health-service delivery. The implementation of these programs had varying degrees of success and failure. In the future, PHC will need to address to critical concerns, the first of which is how to address the pressing health issues of the early 21st century, including climate change, control of noncommunicable diseases, global health emergencies, and the cost and effectiveness of humanitarian aid in the light of increasing violent disturbances and issues around global governance. The second is how PHC will influence policies emerging from the increasing understanding that health interventions should be implemented in the context of complexity rather than as linear, predictable solutions.