Fundamental to primary health care is the need to provide adequate environmental health services to the population. Such services constitute primary prevention, and, under some circumstances, may have a greater impact on health than the provision of personal health services. This study aimed to assess the availability of environmental health services among blacks living in urban and peri-urban areas of South Africa. A stratified random sample of 800 households was selected. After discussions with the Urban Foundation, it was felt that the proportion of informal dwellings obtained (20%) underestimated the true figure, which was closer to 50%. For that reason estimates are presented for a range of values (20-50% informal dwellings). For environmental health services the percentage availability was 30-45% for reticulated water in the home; 18-29% for an inside flush toilet; and 48-62% for possession of a personal refuse receptacle. Data obtained on domestic fuel use indicated that 41-61% of households had electricity. General indicators of social class showed that 62% of households had a monthly income less than R400, and that 22-30% of mothers with children under 5 years of age had an educational level of less than Standard 5. All of the measures were substantially worse among people living in informal dwellings. The data indicate that urgent attention should be given to improving the foundations of primary health care, particularly by providing and giving attention to equity, intersectoral co-ordination and community participation in the provision of essential environmental health services.