Preparing vegetables with heat the contents of their constituents will change to a various extent. Particularly the water-soluble and the heat-sensitive vitamins are affected. At an early stage the vitamin C losses were investigated, because of vitamin C's indicating function for oxidation and leaching-out processes (1, 2, 7, 11-13, 15, 17). The degree of vitamin losses is influenced by various factors, for example the type of food, variety of vegetables, the way of cutting, preparation, duration and method of cooking. The influence of the various cooking methods with regard to the losses of certain water-soluble vitamins will be discussed.