[The population of the big university hospitals in Belgium from the early nineteenth century to the end of the twentieth century].

This paper is the synthesis of researches concerning the university hospitals of Gand, Liège and Louvain in Belgium. First, you will find an abstract of the analysis and main results. The interpretation topics are then approached with three different points of view: the sources, being hospital or medical records, their qualities and their limits; the structure of the institutions and their consequences on the social structure of the patients; the impact of the demographic transition. The hospital, which was one reserved to poor adults, has progressively been authorized to "non-profitables", children first, then old people, so that the ageing of patients largely exceeds that of the population itself.