The twentieth century has witnessed an extraordinary victory over infant and child mortality. This process accelerated after the Second World War. The advances were achieved first mainly in post-neo-natal mortality, then, from the 1960s, came a rapid fall in early neo-natal mortality. The fall in post-neo-natal mortality was without any doubt the result of improved living conditions and of increasingly effective action against infectious and respiratory diseases. From the end of the 1960s, the continued fall in infant mortality resulted primarily from better medical care during pregnancy and birth, and the considerable progress in neo-natal care techniques. The level is now so low that there can be only limited scope for future progress. However, child survival could further be improved by a reduction in the still significant social and geographical differentials.