The deterioration of <i>dosa</i>-sized <i>washi</i> was studied. * 2Dosa*1 is a mixture of animal glue and alum used as a sizing material for Japanese papers. Deterioration rates of tensile strength (breaking length) and tensile energy absorption (TEA) were calculated and compared with that of folding endurance. Since these three values are found to be well correlated, the former values can be used as indices of permanence of <i>washi</i>, and the deterioration rate of tensile energy absorption is a superior index than that of tensile strength, because TEA is more practical in measuring and scattering of data is small. Carbohydrate compositions of <i>washi</i> were also measured by the alditol acetate method. The amount of carbohydrate in the <i>washi</i>, however, showed little change after aging treatment. -- AATA