Alterations in the renal metabolism and/or actions of endothelin-1 (ET-1) may be involved in the pathogenesis and maintenance of essential and renal parenchymal hypertension. ET-1 has the potential to modify a broad range of renal functions involved in controlling systemic blood pressure. First, the kidney clears a large percentage of ET-1 from the blood; decreased renal ET-1 clearance may contribute to hypertension occurring in the setting of chronic renal failure. Second, ET-1 potently constricts the renal vasculature resulting in increased fluid retention and possibly contributing to glomerular sclerosis; enhanced renal vascular and glomerular ET-1 production and target cell actions may play a role in essential hypertension or hypertension accompanying chronic renal failure, cyclosporine administration, or erythropoietin therapy. Lastly, ET-1 is also an autocrine inhibitor of collecting duct sodium and water reabsorption; reduced nephron ET-1 production may result in fluid retention in essential hypertension. Determination of the true role that ET-1 plays in the pathogenesis of the varied forms of hypertension awaits the development of safe, potent, and specific endothelin antagonists.