In 1976 the Ministry of Health of Nicaragua began a low cost program to deliver simple health services in rural areas through trained traditional birth attendants or "parteras." After two years the program had prepared 768 parteras in a five-day training course. Parteras were equipped with a kit that included oral rehydration salts, an antihelminthic, multi-vitamins with iron, aspirin, contraceptives, and obstetrical equipment. The difficulties encountered in implementing this limited set of simple health services illustrate a number of potential obstacles to the achievement of universal, comprehensive primary health care in less developed countries. The most prominent difficulties involved elements of the health service delivery system itself: supervision, the collection and use of management information, training, partera selection, and logistics. The experience also provided examples of issues in the design of delivery systems that require specific applied research.