In the context of a European-funded sixth framework project called AIM, a dynamic microsimulation model MIDAS is being developed for Belgium, Germany and Italy. This is a joint effort by three institutions, the German DIW, the Italian ISAE and the Belgian FPB. This model MIDAS simulates future developments of the adequacy of pensions, following wherever possible the projections and assumptions of the Ageing Working Group.  This paper describes the model MIDAS in detail. It next presents and discusses some simulation results for Belgium, Germany and Italy. Finally, the simulation results of two alternative policy scenarios are presented and discussed.