Grafting of a new carbohydrate UV-reactive molecule, an azidophenyl lactamine (AzPhLac), was achieved on fibers of three different diameters: 12, 18, and 32 microm. Adsorption of AzPhLac on fibers was obtained by using the dip-coating method in solution. The effect of the solution concentration on surface density and yield of grafted AzPhLac was investigated. Surface densities in the range 3-67 nmol/cm2 were obtained without marked difference related to the diameter of the fiber. Quantitative grafting was obtained with a surface of fiber of 1 cm2 and the lowest concentration (0.5 mM) of AzPhLac solution. The surface density and grafting yield decreased with the available surface of the fibers. This phenomenon could be attributed to a masking core-shell effect with outer fibers in the shell preventing the UV grafting of the fibers located in the core of the fibers' bundles. Scanning electron (SEM) and atomic force (AFM) microscopic observations suggested that homogeneous grafting might be obtained.