Opinions about the impact of dietary salt on blood pressure have dominated the debate regarding ‘salt sensitivity', which can be broadly defined as the blood pressure response to changes in sodium intake among individuals in a population. However, the larger question is whether salt consumption exerts significant biological effects independent of changes in blood pressure. Provisional answers to this question are reviewed based on newly discovered links between sodium metabolism and the generation of reactive oxygen species. These links suggest that, in a subset of the general population, salt consumption is a determinant in cardiovascular ageing.