ONDRAF/NIRAS – the Belgian radioactive waste management agency – has published in 2001 the SAFIR 2 report on request of the authorities. The SAFIR 2 report is to be considered as a state-of-the art report and not as a complete safety case. This report gives an overview of the Belgian R&D program related to the geological disposal of HLW and ILW for the period 1990–2000 in the Boom Clay (reference host rock). The three main outcomes of the SAFIR 2 report on which this paper will be more specifically focusing, are the following (including results reported after 2000): long-term safety functions, confirmation of the role of the Boom Clay formation as the main barrier and identification of practical difficulties with respect to technical feasibility (repository design).