Deriving from positive effects of whey drinking cures in antiquity, the Middle Ages and modern time, a review is given on nutritional significance of whey. The proteins are essential components of whey and belong to the proteins with highest biological value because of their amino acid composition. Besides, they show fundamental functional properties, which enable a varied application in foods, dietetic foods and beverages in form of different whey products (powder, protein concentrates and isolates). Whey proteins have found considerable usage in infant's nutrition as whey predominant formulas as well as whey protein hydrolysates in case of cow's milk protein intolerances. A recent field of research are biological active peptide sequences which become effective during digestion and are of importance for secretion of entero hormones as well as for immune enhancing effects. They may contribute to assess the biological value of whey proteins under enlarged points of view and to develop new application forms and areas. It is pointed to further fields of application (e.g. adipositas, gout, kidney insufficiency). Concerning the quantitatively most dominant lactose in whey, it is dealt with its importance for the healthy development of infants (adaptation to the increased lactose content of mother's milk) as well as with lactose intolerance and galactosaemia. In case of mineral salts of whey it is emphasized the high nutrient density of calcium (prophylaxis for osteoporosis), the beneficial Ca:P and Na:K proportions (antihypertensive in case of the last one), the promotion of absorption of mineral salts by lactose, and the high content of iodine. The whey is rich in B-vitamins, which contribute essentially for their satisfaction or requirement in case of a corresponding consumption. To be emphasized is the vitamin B12 in milk and whey, which is the sole source of this indispensable nutrient for blood-formation and cell division in lacto-ovo-vegetarian nutrition. In conclusion, a summarizing dietetics valuation of whey is performed.