Essential medicines, as defined by the World Health Organization (WHO) are "those drugs that satisfy the health care needs of the majority of the population; they should therefore be available at all times in adequate amounts and in appropriate dosage forms, at a price the community can afford."^{[citation needed]}

The WHO has published a model list of essential medicines. Each country is encouraged to prepare their own lists taking into consideration local priorities. At present over 150 countries have published an official essential medicines list. The WHO List contains a core list and a complementary list.

The core list presents a list of minimum medicine needs for a basic health care system, listing the most efficacious, safe and cost-effective medicines for priority conditions. Priority conditions are selected on the basis of current and estimated future public health relevance, and potential for safe and cost-effective treatment.

The complementary list presents essential medicines for priority diseases, for which specialized diagnostic or monitoring facilities are needed. In case of doubt medicines may also be listed as complementary on the basis of consistent higher costs or less attractive cost-effectiveness in a variety of settings.

James Jude Orbinski, OC, OOnt, MSC (born 1960 in England) is a Canadian physician, writer, and humanitarian activist. He is an associate professor of Medicine at the University of Toronto and a Fellow at the Munk School of Global Affairs. In January 2011, he also assumed the Chair of Global Health at the Dalla Lana School of Public Health, University of Toronto. He was President of the International Council of Médecins Sans Frontières (MSF, aka Doctors Without Borders) at the time the organization received the 1999 Nobel Peace Prize. James Orbinski also is the co-founder and Chair of the Board of Directors of Dignitas International, a medical humanitarian organization working with communities to increase access to life-saving treatment and prevention in areas overwhelmed by HIV/AIDS. He is a strong advocate for increasing the availability of anti-retroviral drugs to combat AIDS in poor countries.

He is closely associated with the University of Toronto's Massey College where he is a Senior Fellow and was the founding Saul Rae Fellow. He is considered a brilliant orator.^{[citation needed]} In 1998, Orbinski received the Governor General's Meritorious Service Cross for his work as the MSF Head of Mission in Rwanda during the 1994 genocide. In 2009, Orbinski became an Officer of the Order of Canada and in the citation was recognized by the Governor General as an advocate for those who have been silenced by war, genocide and mass starvation.