THE RESPONSE of individuals with essential hypertension to an acute salt load has been extensively studied.1-5 The response to salt loading in hypertension due to renal artery stenosis, however, has not been well characterized. Recently, Birchall, Madsen, and Anderson," demonstrated that salt loading would magnify the difference in U sodium/U creatinine ratios in unilateral renal artery stenosis.The purpose of this investigation was to study the effect of salt loading on the total urinary output and on sodium excretion in patients with hypertension due to renal artery stenosis. Materials and MethodsThirty-three subjects were studied. They were divided into the following groups: group 1, normal subjects-20 cases; group 2, essential hypertensive subjects-16 cases; group 3, subjects with hypertension due to renal artery stenosis-7 cases. Patients were selected for this study on the basis of the following criteria. All hypertensive patients, once selected and tested, were included in the data presented. The hypertensive patients all had sustained hypertension; during their hospital stay blood pressures were taken four times daily, in the supine and standing positions. The criteria for inclusion in the study were as follows:1. The patient must have been on a normal salt intake and have taken no antihypertensive medications for at least 2 weeks prior to the test. It has previously been established that salt deprivation abolishes the exaggerated response to salt loading in essential hypertension.7