The present study will examine three common premises in the field of international public health: that the primary care services offered by agencies of the Ministries of Health (MH) are less costly than those offered by Social Security institutions, that the former services are inferior to the latter, and that funds are distributed more equitably by the MH centers among their various recipient populations. The 1986 study compared the costs, quality, and equity of the services in 15 primary care centers in Ecuador--eight Ministry of Health centers and seven rural Social Security (RSS) centers--examining budgetary data from 1985 and obtaining information through a questionnaire and interviews with the personnel at those centers. Average costs were calculated by standardized accounting techniques, and it was confirmed that for several important services, especially medical consultations, these costs were much lower in the Ministry centers than in the Social Security centers. However, no differences in the cost of dental care were detected. The evaluation of quality, based on an analysis of the production structure and process, did not yield uniform results. On the one hand, the distribution of personnel and the allocation of funds for drugs and other supplies indicated that the RSS agencies provided better quality services. On the other hand, a questionnaire revealed that the MH health workers' knowledge of various principles of primary care was superior to that of the RSS workers. Upon comparing the per capita budget of the two types of entities, it was confirmed that the Ministry of Health had more equitable per capita coverage than rural Social Security. The implications of these findings for Ecuador and other developing countries are discussed and several recommendations made.