Dietary salt and blood pressure. A perspective. Although dietary salt restriction is often valuable as sole or adjunctive therapy of hypertensive disorders, it is abundantly clear that hypertensive patients comprise a heterogeneous group with regard to salt sensitivity of blood pressure. This is apparent despite the many methodological obstacles to defining salt sensitivity in an individual patient. Currently, dietary trial is the only sure means of defining a given patient as responsive to salt restriction. Easily definable markers of salt sensitivity would allow appropriate targeting of this rather ponderous therapy. Promising leads include the assessment of membrane ion transporters such as sodium-lithium exchange and of the activity of the renin-angiotensin system, including the phenomenon of "non-modulating" hypertension and other volume regulatory hormones such as atrial natriuretic factor. Although less intensively studied than in hypertensive patients, the blood pressure response of normal subjects to salt restriction is also marked by great variability. Given the possibility of deleterious consequences of population-wide salt restriction for at least some people in a setting such as the United States, it seems imprudent to recommend such a policy before its proven worth has been demonstrated by clinical trial. Pending such evidence and the development of markers, salt restriction should be reserved for those in whom it is of demonstrated efficacy. 