Current recommendations for a population-wide decrease in dietary salt consumption come from a conclusion that a substantial portion of the population with essential hypertension is salt-sensitive. It is difficult to determine the appropriateness of these recommendations because of critical gaps in knowledge of the salt-blood pressure relation. There is no agreement on a definition of salt-sensitive blood pressure changes. There is no consensus about mechanisms of changes; several have been suggested but none seems universal. In fact, differing results suggest marked heterogeneity in the mechanisms of salt-sensitive hypertension, and some evidence points to the possibility that arterial pressure of hypertensive subjects is controlled differently than that of normotensive subjects during manipulation of salt intake. Because salt-sensitive blood pressure changes are not always related to the magnitude of the positive sodium balance, it seems possible that for some people the current recommendations for modest dietary sodium restriction may be inadequate to influence blood pressure control for the prevention of hypertension.