We have reported preliminary biological properties of mutant, G72-8, derived from Chinese hamster lung cells (Onoda, 1980 1)): the mutant is characterized by low adhesion to substratum, round shape, increase in spontaneous aggregation, and decrease in growth rate and these altered properties restored to normal by addition of GlcNAc. In this study, when L-fucose was used as radioactive precursor, the rate of L-fucose incorporation into macromolecules was markedly stimulated by addition of GlcNAc to the mutant. Lactoperoxidase-catalyzed iodiation of the cell surface shows that the high-molecular weight cell surface protein detected in the parent cells was reduced on the mutant and restored reversibly to normal by addition of GlcNAc. A random migration of the mutant cells also was reverted to the directional moving of the parent cells by addition of GlcNAc. Our results suggest that the carbohydrate moieties of cell surface proteins has an important role in biological cell behavior, including in adhesion and directionality in cell locomotion