The growing concern regarding the threat to human health posed by mercury in the environment has prompted the Swedish Government to plan for disposal of mercury-containing waste in deep geologic formations. The purpose of the present 3-year project is to determine the major prerequisites and evaluate the feasibility of utilising bentonite barriers for such a purpose. The scope of the present paper is to present the results from the work carried out during the first year. The design concept should be such that the excellent materials properties of high-density bentonite can be utilised. Also, the chemistry should be adjusted in such a way that any deterioration of bentonite becomes tolerable, and such that the mercury species in solution either appear in low concentration, or in a form that has a low mobility. It is concluded that safety analyses may be based on modelling of the speciation in combination with diffusion through bentonite in one dimension. The results of such modelling will be compared with actual migration data from actual waste forms comprising highly compacted mixtures of spent mercury-containing batteries and bentonite.