BACKGROUND: Socio-economic inequalities in health survey participation can jeopardize the extrapolation of the survey findings to the total population. Earlier research, based on aggregated data, showed that in Belgium less-educated people with poor health were less likely to participate in a health survey. In this article, the association by socio-economic status and household non-response in a health survey is examined. METHODS: A linkage between the Belgian Health Survey 2001 with Census 2001 enabled us to evaluate the participation by socio-economic status. RESULTS: We observed that the socio-economic position was a determinant of health survey participation: participation rate was significantly lower in households with a lower socio-economic profile. CONCLUSION: Socio-economic inequalities in participation can introduce a bias in the health survey findings. Strategies targeting improvement of the participation of lower socio-economic groups need to be considered