BackgroundThis study addresses educational inequalities in young-adult mortality between the 1990s and the 2000s by comparing trends in the three different regions in Belgium stratified by sex. Social inequalities in mortality are of major concern to public health but are rarely studied at young ages. Substantial health differences have been found between the Flemish (FR) and Walloon region (WR) concerning (healthy) life expectancy and avoidable mortality, but little is known about regional differentials in young-adult mortality, and comparisons with the Brussels-Capital Region (BCR) have thus far never been made.MethodsData are derived from record linkage between the Belgian censuses of 1991 and 2001 and register data on death and emigration for the periods 01/03/1991-01/03/1999 and 01/10/2001-01/10/2009. Analyses are restricted to young adults aged 25 to 34 years at the moment of each of the censuses. Absolute (directly standardized mortality rates (ASMRs)) and relative (mortality rate ratio using Poisson regression) measures were calculated.ResultsThere is a significant drop in young-adult mortality between the 1990s and the 2000s in all regions and both sexes, with the strongest decline in the BCR (e.g. ASMR of men declined from 165.6 [151.1-180.1] per 100,000 person years to 73.8 [88.3-98.3]). The mortality rates remain highest in the WR in the 2000s Between the 1990s and the 2000s, a remarkable change in the educational distribution occurred as well, with much lower proportions of primary educated in all regions in the 2000s in favour of higher proportions in all other educational levels, especially in higher education. All educational groups show lower mortality over time, except for lower educated men in the FR.ConclusionsThere is a positive evolution towards lower mortality among the young-adult Belgian population. The WR trails behind in this evolution, which calls for tailored preventive actions. Educational inequalities are marked in all regions and time periods. A more general discussion is needed on the responsibility of society in rendering support and capability to enhance the state of well-being of those not able to achieve a high social position.Electronic supplementary materialThe online version of this article (doi:10.1186/s13690-014-0059-3) contains supplementary material, which is available to authorized users.