For over 15 years the Centre for Social Policy at the University of Antwerp has been involved in research on social security. More specifically, it has tried to develop research methodologies which would make it possible to quantify the adequacy of the social security system in Belgium, and to assess its impact on the income of households. The first part of this article provides a broad outline of the social security system in Belgium. The second and major part presents the main results of the research. The same methodology and the same standardised presentation of results is currently being used in a comparative study financed by the Commission of the European Community and undertaken by research groups in Belgium, the Netherlands, Luxembourg, France, Ireland, Spain and Greece.