This volume contains papers presented at the First International Symposium on Mechanism and Treatment in Essential Hyperten­ sion, which was held on October 23 and 24, 1985 in Nagoya, Japan. The meeting was an official satellite symposium to the meeting of the Fifth International Symposium on Rats with Spon­ taneous Hypertension and Related Studies in Kyoto, October 20-22, 1985. The Nagoya symposium was made possible by offi­ cial grants from the city of Nagoya and Aichi Prefecture and the generous financial support of many companies. The aim of the symposium was to provide a forum for presen­ tation and discussion of recent advances in the area of essential hypertension, particularly with regard to calcium mechanisms in vasoconstriction and vasodilation in arterial vessels and the func­ tion of arterial smooth muscle. The role of calcium ions in the function of arterial smooth muscle has attracted a great deal of attention in the last two decades. The mode of action of calcium ions was revealed at the molecular level. The hypertension model of the spontaneously hypertensive rat has been widely utilized for research into the fundamental mechanisms of genetic hyperten­ sion, stroke, and cardiovascular disease as well as into therapeutic measures. New tools of calcium agonists and antagonists have become available to research into the mechanism, prevention, and treatment of essential hypertension at the molecular, subcellular, and cellular levels of arterial smooth muscle, at the organ level of arterial vessels, as well as at the total systemic level.