Autoradiography was used to determine the distribution of labeled sugar in conducting elements of the blade and petiole of sugar beet leaves at intervals ranging from 5 sec to 24 hr. The processes of assimilation by the green cells, collection of sugar in the minor veins and export in phloem elements were demonstrated visually. It appears that in minor veins sugar is translocated in companion cells rather than sieve tubes. In major veins translocation occurs in sieve tubes.