The objective of this work has been to develop a procedure for the determination of the concentration of chitosan in powder samples, by capillary viscosimetry of Ostwald (capillary of 0.55 ± 0.02 mm internal diameter). Standard chitosan solutions between 461 mg/liter up to 9138 mg/liter and pH 1.24 were prepared for all cases. Tests were also carried out at temperatures between 20° to 50°C, observing linearity with the concentration until before 9138 mg/liter. The most important dependence was the relative viscosity (ηr) versus the concentration (concordant with the Poiseuille equation) which in the range 461 mg/liter to 2808 mg/liter gave a linear dependence with r2= 0.995, enabling the analysis of samples for the content of chitosan with consistent results and comparable with the referentials.