This article presents and critically discusses evidence on the determinants of mortality reductions in developing countries. It argues that increases in life expectancy between 1960 and 2000 were largely independent of improvements in income. The author characterizes the age and cause-of-death profile of changes in mortality and assesses what can be learned about the determinants of these changes from the international evidence and from country-specific studies. Public health infrastructure, immunization, targeted programs, and the spread of less palpable forms of knowledge all seem to have been important factors. Finally, the article suggests that the evolution of health inequality across and within countries is intrinsically related to the process of diffusion of new technologies and to the nature of these new technologies, public or private.