A main goal of the World Health Organization (WHO), as expressed in the Alma-Ata Declaration of 1978, is to provide to all the citizens of the world a level of health that will allow them to lead socially and economically productive lives by the year 2000. By the late 1980s, however, vast disparities in health care still existed between the rich and poor countries of the world. In developing countries such as Ethiopia, Guinea, Mali, and Mozambique, for instance, governments in the late 1980s spent less than $5 per person per year on public health, while in most western European countries several hundred dollars per year was spent on each person. The disproportion of the number of physicians available between developing and developed countries is similarly wide.

Along with the shortage of physicians, there is a shortage of everything else needed to provide medical care—of equipment, drugs, and suitable buildings, and of nurses, technicians, and all other grades of staff, whose presence is taken for granted in the affluent societies. Yet there are greater percentages of sick in the poor countries than in the rich countries. In the poor countries a high proportion of people are young, and all are liable to many infections, including tuberculosis, syphilis, typhoid, and cholera (which, with the possible exception of syphilis, are now rare in the rich countries), and also malaria, yaws, worm infestations, and many other conditions occurring primarily in the warmer climates. Nearly all of these infections respond to the antibiotics and other drugs that have been discovered since the 1920s. There is also much malnutrition and anemia, which can be cured if funding is available. There is a prevalence of disorders remediable by surgery. Preventive medicine can ensure clean water supplies, destroy insects that carry infections, teach hygiene, and show how to make the best use of resources.

In most poor countries there are a few people, usually living in the cities, who can afford to pay for medical care, and in a free market system the physicians tend to go where they can make the best living; this situation causes the doctor–patient ratio to be much higher in the towns than in country districts. A physician in Bombay or in Rio de Janeiro, for example, may have equipment as lavish as that of a physician in the United States and can earn an excellent income. The poor, however, both in the cities and in the country, can get medical attention only if it is paid for by the state, by some supranational body, or by a mission or other charitable organization. Moreover, the quality of the care they receive is often poor, and in remote regions it may be lacking altogether. In practice, hospitals run by a mission may cooperate closely with state-run health centres.

Because physicians are scarce, their skills must be used to best advantage, and much of the work normally done by physicians in the rich countries has to be delegated to auxiliaries or nurses, who have to diagnose the common conditions, give treatment, take blood samples, help with operations, supply simple posters containing health advice, and carry out other tasks. In such places the doctor has time only to perform major operations and deal with the more difficult medical problems. People are treated as far as possible on an outpatient basis from health centres housed in simple buildings; few can travel except on foot, and, if they are more than a few miles from a health centre, they tend not to go there. Health centres also may be used for health education.

Although primary health-care service differs from country to country, that developed in Tanzania is representative of many that have been devised in largely rural developing countries. The most important feature of the Tanzanian rural health service is the rural health centre, which, with its related dispensaries, is intended to provide comprehensive health services for the community. The staff is headed by the assistant medical officer and the medical assistant. The assistant medical officer has at least four years of experience, which is then followed by further training for 18 months. He is not a doctor but serves to bridge the gap between medical assistant and physician. The medical assistant has three years of general medical education. The work of the rural health centres and dispensaries is mainly of three kinds: diagnosis and treatment, maternal and child health, and environmental health. The main categories of primary health workers also include medical aids, maternal and child health aids, and health auxiliaries. Nurses and midwives form another category of worker. In the villages there are village health posts staffed by village medical helpers working under supervision from the rural health centre.

In some primitive elements of the societies of developing countries, and of some developed countries, there exists the belief that illness comes from the displeasure of ancestral gods and evil spirits, from the malign influence of evilly disposed persons, or from natural phenomena that can neither be forecast nor controlled. To deal with such causes there are many varieties of indigenous healers who practice elaborate rituals on behalf of both the physically ill and the mentally afflicted. If it is understood that such beliefs, and other forms of shamanism, may provide a basis upon which health care can be based, then primary health care may be said to exist almost everywhere. It is not only easily available but also readily acceptable, and often preferred, to more rational methods of diagnosis and treatment. Although such methods may sometimes be harmful, they may often be effective, especially where the cause is psychosomatic. Other patients, however, may suffer from a disease for which there is a cure in modern medicine.

In order to improve the coverage of primary health-care services and to spread more widely some of the benefits of Western medicine, attempts have sometimes been made to find a means of cooperation, or even integration, between traditional and modern medicine (see above Medical practice in developing countries: India). In Africa, for example, some such attempts are officially sponsored by ministries of health, state governments, universities, and the like, and they have the approval of WHO, which often takes the lead in this activity. In view, however, of the historical relationships between these two systems of medicine, their different basic concepts, and the fact that their methods cannot readily be combined, successful merging has been limited.