Halite cementation in porous sandstone from the Lower Triassic Bunter Formation in North-West Germany has been studied using measurements of porosity and permeability, before and after salt extraction, as well as from petrographic observations. The results show that in cemented sandstones there is a clear tendency for the larger pores to be halite-®lled while the smaller pores, which are responsible for the residual porosity, are left empty. Observations on cemented`pin-stripe' aeolian sandstones, in which laminations of ®ne and coarser sand grains alternate on a millimetre scale, indicate that this selective cementation is not due to differences in the brine composition in the pores. The implication, which is also supported by other observations, is that¯uids in small pores can maintain a higher supersaturation with respect to crystallization.