The present work presents a study on the grafting of polyurethane onto chitosan. Prepolymers (polyurethanes) were obtained by condensation reactions between poly(ethylene glycol) of two different molar masses and isophorone diisocyanate. Characterization of graft copolymers was performed by infrared spectroscopy (IR) and 13 C Nuclear Magnetic Resonance in the solid state (13 C NMR). Evidences of grafting were obtained by IR from the absorbance increase of relative intensity of NH and CO bands, with respect to chitosan. The degree of NH2 substitution by urea groups observed from 0.12to 0.59 was estimated from NMR data. The graft copolymers exhibited different solubility behavior as a function of degree of substitution, such as partial solubility, gelation or swelling in diluted acetic acid, and swelling in water, dimethylsulfoxide and acetic acid/sodium acetate.