A novel method for the preparation of 4-O-methyl-D-glucuronic acid is described. This sugar and 4-O-methyl-D-glucose were obtained in good yield by two different series of reactions from 2-O-(4-O-methyl-D-glucopyranuronosido)-D-xylose, an acid hydrolysis product of the hemicellulose of Populustacamahacca Mill.