The significance and substance of this symposium is based upon highly impressive development: In 1955 Otto H. Gauer and James P. Henry were able to demonstrate that volume increments of the left atrium of the heart led to increased renal sodium and water excretion, a phenomenon which was considered to indicate the existence of volume regulation. Since Paintal found increased electrical activity in afferent vagus fibres from these stretched left atrium, the diuretic response was attributed to inhibitory effects on ADH secretion coming about via the integrating action of the hypophysis. Never at this time in the late 50’s, neither Gauer himself nor his associates (myself included) at the Kerckhoff Institute in Bad Nauheim, Germany, nor any scientist arguing about the results of Gauer, with Gauer, came up with the idea that the hormone being produced by the heart itself might be involved in the regulatory process. It must be assumed, that the specific granules in close vicinity of the artrial muscle fibers described by Kisch, also in 1955, were either not known to or neglected by physiologists and clinicians. Eventually, the break came 25 years later in 1980 when De Bold and Sonnenberg, who is present today, and coworkers and associates, injected extracts of rat atria into rats and observed the significant diuresis and natriuresis. Since it was evident to them that the granules behaved like a depository of a hormone, it was consequently concluded that the heart pump does operate as an endocrine gland as well. The publication of De Bold, Sonnenberg and others was followed by competitive and stimulating research activities in many countries of the world. The atrial natriuretic peptide was quickly isolated, it’s amino acid sequence was determined and it’s mechanism of action could be characterized. Up to now there is conclusive evidence that besides its natriuretic and diuretic action, ANP leads to vasodilatation and inhibits renin and aldosterone secretion.