What is the impact of technology on improving the life situations of people, especially the poor? How is this impact analyzed in terms of health improvements? These questions are paramount in the minds of health planners as they pursue national policies of primary health care, a policy popularized by the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) and accepted by over 150 governments at Alma Ata in 1978. The purpose of this paper is to explore these questions in depth. It begins by giving the background to the debate, then examines the origins of two concepts which have dominated the field, those of 'primary health care' and 'selective primary health care.' On this basis it suggests areas of differences in the two concepts and discusses the policy and practical implications of confusing the two approaches. The paper suggests that the differences are firstly who controls the outcome of technological interventions and the perceived time frame in which plans can be carried out.