Merck is a global research-driven pharmaceutical company that, throughout its history, has devoted considerable effort to bringing its medicines, vaccines, expertise and experience to people in need around the world. Its primary responsibilities are: to discover, develop and deliver innovative medicines and vaccines that address major burdens of illness globally and/or address specific poor or vulnerable groups; to develop long-term business models that help its products reach as many people as possible; and to promote and participate in partnerships with governments, multilateral and non-governmental organizations, other private-sector organizations and communities, to build healthcare capacity and to address specific health and development challenges around the world. Merck believes that responding to global health challenges is a strategic and humanitarian necessity and that, through public-private partnerships, significant progress can be achieved. Twenty years ago, in October 1987, before collaboration between public and private sectors was common, Merck launched the Mectizan Donation Program (MDP) - a unique, multisectoral coalition involving Merck, the Mectizan Expert Committee (MEC), the Task Force for Child Survival and Development, the World Health Organization (WHO), the World Bank, the United Nations Children's Fund, national ministries of health, more than 35 non-governmental development organizations, and thousands of local community healthworkers - to treat a debilitating, disfiguring and often blinding disease called onchocerciasis (river blindness). Through this programme, Merck made the commitment to donate Mectizan (ivermectin) for as long as needed and wherever needed, to combat this disease. Since the MDP's inception in 1987, Merck has donated >1800 million tablets of Mectizan, with >530 million treatments for onchocerciasis administered since 1987. The programme currently reaches >68 million people in Africa, Latin American and Yemen annually, via community-based treatment programmes in 125,000 communities in 33 endemic countries. This 20-year-old effort has achieved a number of notable results, including positive health impacts, economic benefits, strengthened health systems, and the empowerment of communities where the delivery and administration of Mectizan are managed. The MDP serves as a model for similar health programmes in the developing world and has also laid the foundation for the current integration efforts around 'neglected' tropical diseases. It has also taught the world many valuable lessons - about how to mobilize resources to address significant health challenges - and has demonstrated that it is possible, through public-private partnerships, to deliver healthcare to long-neglected populations, despite seemingly insurmountable obstacles including inadequate financial and human resources, lack of social, economic and health infrastructures, civil unrest and political strife, and competing, high-priority health issues.