A brittle culm variety, Sekitorisai-No. 1, and a stiff culm variety, Haganemugi (Hordeum sativum, JESSEN) were used to study the relation between YOUNG's modulus (E) and bending rigidity (EI) in internodes and nodes. YOUNG's modulus measured by OLSEN's type stiffness tester, and bending rigidity calculated from YOUNG's modulus and moment of inertia. There was not so great differences of YOUNG's modulus between both varieties, but YOUNG's modulus in Sekitorisai-No. 1 was slightly larger than of Haganemugi. Regarding the position of internodes and nodes, it was recognized that the uppermost position of internode and node had the largest YOUNG's modulus, medium in the base position, and the smallest in the intermediate position. The bending rigidity of Haganemugi is larger than that of Sekitorisai- No. 1, and it is larger in the base position, and on the other hand small in the upper position. The stiffness of culm has relation to the diameter of buckling load, and buckling load is related to the bending rigidity as long as the culm length is constant. In theoretically, YOUNG's modulus and moment of inertia have the same relation to the bending rigidity. In the case of same bending rigidity with the different mome nt of inertia, YOUNG's modulus are larger in culms with smaller moment of inertia, and vice versa. So the increase of YOUNG's modulus is valuable for concering the stiffness of culms with the small moment of inertia. Moment of inertia was determined by the outer diameter and the inner one. A large moment of inertia was regarded in culms with large outer diameter or the with small inner diameter. In the case of the same moment of inertia with different outer and inner diameter, the cross section area of culm tissue was small in culms with large outer and inner diameter than with small outer and inner diameter.