The apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress-relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one-component Maxwell model.