The progress towards the production of salt tolerant plants through selection in cell cultures is briefly reviewed. The need for a fuller understanding of the mechanisms of salt tolerance in non-halophytes is emphasised and illustrated with reference to recent investigations on the role of proline. A clear protective effect, against salt stress, of exogenously applied proline has been demonstrated suggesting elevated levels of endogenous proline synthesis, for which there is a direct selection procedure, as a basis for improved salt tolerance. Salt tolerance of proline-overproducing plants and cell cultures is currently under investigation in a Nicotiana sylvestris line with almost 100-fold increase in free proline.