Traditionally, cities have benefited from a disproportionate share of the resources available for health care and, as a result, most developments in primary health care have been in rural areas. Recently, however, attention has been called to the inequities that exist within cities and to the rapid growth of the urban poor. This paper reviews the topic of primary health care and the urban poor in developing countries. The disease patterns of the urban poor reflect the problems of underdevelopment and industrialization. The few studies that focus upon the health problems of the urban poor demonstrate a prevalence of infectious diseases and malnutrition which is comparable to and often greater than that observed in rural populations. At the same time, however, the urban poor suffer the typical spectrum of chronic and social diseases. The magnitude of the health problems of the urban poor rarely emerges in city health statistics. This is either because the ‘unofficial’ squatters and shanty town or slum inhabitants do not appear in the statistics or because their conditions are obscured by the enormous difference that exists between their status and that of the urban elite. At the community level there is now evidence of relevant, constructive and hopeful approaches to helping the urban poor through primary health care. Although there are few analytical or evaluative examinations of such initiatives, it is possible to identify emerging trends such as the development of neighbourhood health programmes, the use of community health workers and attempts to link hospital services with community health action. It remains to be seen whether the health departments in any cities can bring about the co-ordination and support needed for the improvement of environmental and socio-economic conditions which are fundamental for improving health. Also, international agencies need to focus more attention upon the particular plight of the urban poor.