The First International Symposium on Mechanism and Treatment in Essential Hypertension was held on October 23 and 24, 1985 in Nagoya. The Second International Symposium, which was held on May 30,31, and June 1, 1988 in Nagoya, was a success thanks to the endeavors of all the participants. These symposiums were made possible by the generous support of the city of Nagoya, Aichi Prefec­ ture, and various contributions. Understanding of the mechanisms of gene (major gene, essential) hypertension is impossible unless we comprehend the physiological properties of arterial smooth muscle. Since Langendorff's discovery of the role of calcium ions in muscle contraction in 1895, we have made immense progress in our knowledge of the role of the calcium ion in the excitation-contraction coupling of the arterial smooth mus­ cle. Investigation of the molecular mechanisms controlling the cellu­ lar basis of calcium ion action has been established with the discovery of the calcium binding protein (Ebashi 1963). The participation of the calcium induced calcium mechanism in the contraction of muscle has been directly demonstrated by using chemically skinned smooth muscle fibers (Endo et al. 1977). Methods for intracellular free cal­ cium contents and calcium channel activity have been developed and contribute to the study of the role of the calcium ion in arterial smooth muscle contractility. Such recent progress promotes study of the basic physiological, biochemical, and molecular properties of the calcium channel, and, in the field of hypertension research, the sodium and potassium channels.