By hydrolysis and hydrogenolysis, plant polysaccharides, i.e. mainly cellulose and hemicelluloses, can be converted with high yields into polyhydric alcohols (hexitols, pentitols, glycerol, ethylene glycol, propylene glycol). Procedures which have been developed in the U.S.S.R. are described. Of particular interest is the simultaneous hydrolysis and hydrogenolysis of plant polysaccharides with noble metal catalysts. Here yields are almost quantitative.