It is quite clear that in vitro experiments with pure substrates and highly purified enzyme preparations can do no more than indicate types of possible action. Therefore, already having a method of isolating a barley β-glucosan in a very high degree of purity, means for obtaining enzyme preparations of enhanced purity were sought, and it was hoped, by employing these preparations in the degradation of initially-water-soluble β-glucosan, to provide further evidence of the complex nature of the degradative scheme. Included in this approach are attempts to differentially inactivate endo- and exo- β-glucosanases and cellobiase, and it will be seen that confirmation of an earlier assumption of the mechanism for the degradation of β-glucosan has arisen from this study. Furthermore, chromatographic and ionophoretic analyses of the degradation products of β-glucosan enzymolysis also offer the possibility of deteimining tne manner in which the β-1,3- and β3-1,4- linkages are distributed within the β-glucosan molecule. With the realisation of the important part played by the β -glucosanases in modification, the opportunity has been taken to show some aspects of the behaviour of endo- and exo-β-glucosanases and cellobiase during the course of commercial maltings. During one such series of investigations the water-soluble and alkalisoluble carbohydrates were isolated and analysed with the intention of obtaining sane indication of the manner in which endospermic cell-walls are broken down. At the same time there was the possibility that an opportunity would arise to support or overthrow the theories that either "cellulase" activity of a barley or its green malt or gum content alone or a combination of both gives an indication of the malting properties of a particular barley. Although the main argument is confined to enzymes of raw and geminating barley, the opportunity has been taken to provide some comparisons with the enzymes of other raw cereals.