Reducing the risk of infant mortality is one of the most important issues in developing countries. In today’s developed countries, lowering the infant mortality rate was a major issue during the periods of economic development. Hence, reviewing studies that have analyzed the decline in infant mortality rates in developed countries can provide meaningful suggestions for developing countries. This study outlines the decline in infant mortality rates in Japan, and organizes and discusses the issues associated with the decline in infant mortality rates in other developed countries. Previous studies have focused on a number of factors that can be attributed to declining mortality rates, including studies on the effects of improvements in living standards, on private initiatives aimed at improving the hygiene of individuals and households, and on public health interventions. Recent studies tend to focus more on the third factor. In other words, they emphasize the effects of public and institutional interventions. However, multifarious factors are responsible for the decline in the risk of infant mortality in developed countries. Moreover, we must consider the synergistic effects of various public institutions and programs in the private sector. The most important point is to accurately clarify the questions surrounding the setups employed for the implementation of various interventions, the reasons institutions performed well in interventions, and the extent to which the system impacted infant mortality rates. I believe that accumulating such historical evidence is both a necessary and a valid means for providing meaningful suggestions to today’s developing countries that are grappling with the issue of persistent, high infant mortality rates.