There is now some sort of agreement between different investigators regarding red blood cell Na+ transport in essential hypertension. This concerns at least two points: a) Na+ transport function is abnormal in erythrocytes from an important number of essential hypertensive patients, and b) the population of hypertensive patients is heterogeneous with respect to the different abnormalities in Na+ transport function. In contrast with the very large number of fundamental studies of Na+ transport in erythrocytes from essential hypertensive patients, very little is known concerning the clinical relevance of these findings. This review focuses on the etiopathogenic and pathophysiologic meaning of Na+ transport abnormalities which may be useful to the diagnosis and/or treatment of hypertensive patients.