Extracts of sycamore cambial tissue convert UDP-glucose into UDP-glucuronic acid, and the latter into UDP-xylose and UDP-rhamnose. None of the corresponding galactose series of monosaccharides was formed indicating the absence of epimerases, postulated as an important feature of differentiation. UDP-glucose is formed in greater quantities than any of its nucleoside analogues and it is suggested that UDP-glucose plays a more important role in carbohydrate metabolism in this tissue.