Chitosan membranes were obtained by a casting/solvent evaporation method and cross-linking with sodium tripolyphosphate. The effect of cross-linking time was studied and the cross-linked membranes were characterized with respect to equilibrium water content, sodium content, IR spectroscopy and permeability to a model drug (Estradiol). Sodium content increased with increasing cross-linking time. Equilibrium water content was higher in the membrane with the lowest cross-linking time. This membrane also showed a higher flux of Estradiol compared with the other which exhibited an increment in equilibrium water content and flux of Estradiol with the increase in cross-linking duration. These dissimilar results could be explained by a significant correlation between the hydrophilicity of the membrane and the hydrophobicity of Estradiol.