Two 1,3;1,4-beta-glucan endohydrolases have been purified from extracts of germinating barley by ammonium sulphate precipitation, ion-exchange and gel filtration chromatography. Both enzymes are monomeric, basic proteins. Enzyme I has a molecular weight of 28000 and an isoelectric point of 8.5, while enzyme II has a molecular weight of 33000 and an isoelectric point greater than 10. Enzyme II is a glycoprotein containing 3.6% carbohydrate, of which three residues are probable N-acetylglucosamine, but enzyme I contains only traces of associated carbohydrate. The amino acid compositions of the two 1,3;1,4-beta-glucan endohydrolases are similar and the cross-reactivity of antibodies raised against the purified enzymes suggests that they share common antigenic determinants.