Context and aim In the beginning of the 21st century, life expectancy equals 75.6 years among men and 81.7 years among women in Belgium. These values hide important inequalities between population groups. In our doctoral research significant mortality differences have been shown as a function of socio-economic characteristics (educational level, occupational class and wealth) for Belgium at the beginning of the 1990s. For Belgium, this was the first time that an indisputable quantitative study showed that even in a modern welfare state with a strong social security system major inequalities in mortality remain significant, placing the lower social classes at the short end of the rope. Our research in differential mortality has procured Belgium of no longer being a blind spot in international research in social mortality differentials. Social inequality in mortality has recently gained interest when it became apparent that social rather than medical factors lie at the bottom of large and persistent health and mortality inequalities. In this respect, a number of crucial questions rise in international research. Many questions concern the mechanisms and causes of social mortality differences. An important research question is the reproduction of inequalities from generation to generation and the effect of social mobility. This research is mainly dominated by a limited number of countries that use exceptional administrative databanks (in particular Scandinavian countries) or large surveys (the USA and the UK). For the first time in Belgium we dispose of a databank that can add a crucial contribution to this research. The specific characteristics of our social security and health system supply opportunities that can shed a new light on data that until recently could only be contextualised in the Anglo-Saxon or Scandinavian systems. Moreover, the presence of two large cultural communities in our country offers an interesting line of approach for comparative research that may be useful in the search of intervening mechanisms. Finally, this research has immediate relevancy for the health and welfare policy in our country. A first question that provokes international controversy is whether health and mortality inequalities are increasing or diminishing. This question is pertinent not only because of its social relevancy (the European Community has accepted a program in Lisbon that wishes to tackle inequalities in Europe), but also to gain a better insight in the phenomenon of social inequality in mortality. From this descriptive analysis, we can further explore two important issues about the future evolution and the possible government interventions. The first one concerns the reproduction of social inequalities in mortality and related to this the reproduction of inequalities in health. The new Belgian data allow us to take into account the parental socio-economic position and to investigate whether parental social status has an effect on the individual mortality risks. Moreover, we can also study the effect of intergenerational mobility. In intergenerational mobility, we compare the personal socio-economic position with the parental socio-economic position and explore the effect of positive (or upwards) and negative (or downwards) mobility on mortality risks. The second issue focuses on the life cycle as a process of cumulative opportunities and risks and on the evolution and interaction between social status and health. Besides intergenerational mobility, we can also study the impact of individual mobility, i.e. intragenerational mobility, probably an important player in the differentiation process. International studies usually integrate current socio-economic position in their analyses without taking into account changes in socio-economic characteristics. As a consequence, the impact of social mobility on health has not been mapped very often. As the new Belgian dataset provides information at two points in time, changes in professional class, wealth (defined in terms of housing quality) and marital status can easily be traced. We can thus consider the influence of these transitions on one's life chances. As mortality is usually related to current socio-economic characteristics, the study population is often limited to middle-aged persons for whom it is relatively easy to determine the position in society. The young and the elderly have been investigated less frequently. In this way, it remains unclear whether there exists a lifecycle effect in the impact of socio-economic position on mortality. The availability of socio-economic data at two points in time, with an interval of 10 years, allows an extension of the study population towards younger and older age groups. By including all age groups in this study, we hope to go against the main stream and to present a full picture of inequalities, both among men and women. For the elderly and retired population, the new data imply a large improvement because now information on professional class is available, on top of data on educational level and housing conditions. In this respect, the research project fills an important gap in international research, especially in the light of the high mortality among the elderly.