This paper traces the evolution of the selective primary health care (SPHC) concept, from its presentation at a meeting in Bellagio, Italy, and its subsequent publication in the New England Journal of Medicine in 1979. It reviews the early debate between those in favor of selectivity and those in favor of comprehensive primary health care (CPHC). While this debate was going on, a breakthrough in terms of implementation came with UNICEF's launching of its Children's Revolution in 1982/83, promoting four specific 'social and scientific advances' for improving the health and nutrition of the world's children. They were growth monitoring, oral rehydration therapy, breastfeeding and immunization. Meanwhile the interest of a number of people for achieving 'Health For All' by targeting for action an essential short list of diseases was the impetus for another conference in 1985, Good Health at Low Cost. Through analysis of the achievements of four societies (Cost Rica, China, Kerala and Sri Lanka) efforts were made to define further a prioritized health development strategy, and a number of measures were identified as helping countries achieve good health. While some have argued that SPCH and CPHC are irreconcilable and diametrically opposed, this paper suggests that both SPCH and CPHC are both acceptable. Technology has its place. The field of view of SPHC has enlarged drastically, from individual diseases to the role of other sectors such as education and agriculture. The concept of SPHC has broadened to accept Rifkin's and Walt's assertion that "developmental processes need further exploration and research strengthening capabilities within countries".(ABSTRACT TRUNCATED AT 250 WORDS)