During this century, improvements in fetal and infant mortality have been dramatic in the western world, mainly as a result of improved socio-economic conditions. Relative to many other developed countries, the decrease has been more dramatic in the Nordic countries. Population-based health registries exist in all Nordic countries. By record-linkage between birth registries and census data, it is possible to perform population-based studies on the association between social factors and feto-infant mortality. Such studies have recently been carried out in Denmark, Finland, Norway and Sweden and socio-economic differences in late fetal and postneonatal death rates were seen. Death rates as well as the relative importance of socio-economic factors differed between these countries. In Norway, infants delivered by women with 9 years or less of schooling faced an almost three-fold increased risk of dying postneonatally as compared to infants delivered by women with at least 12 years of education. In order to successfully decrease the socio-economic differences in feto-infant mortality between and within the Nordic countries, it is necessary to analyse possible preventable risk factors that are distributed unevenly not only in different socio-economic groups but also between the Nordic countries.