BACKGROUND: Socio-economic differentials in health are a reality in adults but their postulated persistence throughout the life-course is a subject of discussion. METHODS: Given the real socio-economic inequalities in the health of the adult population in Belgium, we used the 1997 national health survey data to measure these inequalities in the population between the ages of 15 and 24 years, inclusive. Concentration indices were calculated for three health-related variables, namely, subjective health, smoking, and drinking, in connection with various socio-economic indicators specific to the individual and/or the household (occupation, education, income, poverty, socio-economic insecurity). RESULTS: These concentration indices confirmed the existence of socio-economic differentials in the health of these 15-to-24-year-olds in Belgium. The data showed that a "poor health" status for subjective health and smoking was more frequent in the most disadvantaged socio-economic groups and for daily drinking more frequent in the better-off socio-economic groups. CONCLUSIONS: We found a relative diversity in the magnitudes of the inequalities measured depending on the parameters used for their quantification. However, there was an overlapping convergence and reproducibility of the patterns in the general directions of the inequality measurements, as follows: the results for a given indicator were remarkably consistent, regardless of the socio-economic variable studied. This consistency argues in favour of the confirmation of socio-economic class differentials in health in 15- to 24-year-olds in Belgium. ; Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't ; info:eu-repo/semantics/published