Several lines of evidence have implicated the kidney as having a pivotal role in the pathogenesis of essential hypertension. Whatever the initiating factors in an individual patient, it is becoming clear that a renal response must be involved to sustain the elevated blood pressure. There are a number of suggested mechanisms by which the kidney may influence arterial blood pressure. The importance of fluid volume and the role of sodium renal perfusion in elevated blood pressure has been well established. Recent investigations have suggested that sodium and calcium transport defects may exist in patients with essential hypertension. The accumulation of sodium can lead to calcium accumulation; calcium may therefore play an important role in the development of hypertension. Since the key role played by calcium ions in many biologic processes has been recognized, the role of calcium on peripheral vessels as well as the microvasculature of the kidney has become an area of stimulating and exciting research efforts.