A simple and objective method was developed of evaluating the mechanical property of the vocal fold in relating to stiffness by analyzing stress-strain curves. Stiffness of the true and false vocal fold was examined in human and canine excised larynges under various conditions.1) Stiffness of the membranous portion of the vocal fold was least at the middle and greater around the anterior commissure and vocal process. Stiffness of the false vocal fold was much less than that of the true vocal fold.2) As vocal fold tension increased, stiffness of the vocal fold increased.3) Stiffness of the vocal fold was decreased and hysteresis was increased when the thyroarytenoid (vocalis) muscle contracted.