A novel approach for chemical modification of carbon nanotubes was developed, which involved radio frequency glow-discharge plasma activation, followed by chemical reactions characteristic of the plasma-generated functional groups. For instance, amino-dextran chains have been immobilized onto acetaldehyde-plasma-treated aligned carbon nanotubes through the formation of Schiff-base linkages, which were further stabilized by reduction with sodium cyanoborohydride. Using the same reaction, we have also chemically grafted periodate-oxidized dextran chains pre-labeled with fluorescein onto ethylenediamine-plasma-treated carbon nanotubes. The fluorescein labeling allows the surface immobilization reaction to be followed simply by photoluminescence measurements. The resulting polysaccharide-grafted carbon nanotubes are very hydrophilic, as demonstrated by X-ray photoelectron spectroscopic and air/water contact angle measurements.