buckling criterion is established and, furthermore, a simple for­ mula for buckling criterion with reasonable accuracy for engi­ neering purposes is obtained. Special attention is paid to exactly satisfying the boundary conditions, and the solution thus obtained is compared with that of Klosner and Forray.1 This paper is a brief report on reference 2. The ideas and the principles of the author's method are: first, by the use of Duhamel's analogy, the thermal-stress problem can be converted into the isothermal problem subjected to an appro­ priate imaginary hydrostatic pressure and imaginary body forces; secondly, two-dimensional plane-stress problems involving body forces can be solved rigorously by the principle of virtual dis­ placements provided the displacements are given at the edges; and finally, these displacements expressing the boundary condi­ tions can be so defined that the conservation of the straightness of the edges after heating may be satisfied. The stresses obtained in this manner can be used in calculating the buckling criterion of the plate. The displacements in the plane of the plate may be expressed as By inspecting the boundary conditions imposed on the prob­ lem, the validity of the solutions by Klosner-Forra y and the author can be shown. The Klosner-Forray solution will be exact when the tensile rigidity of the web is zero, while the author's solution will be exact when it is infinitely large. In the region located between these two limiting cases, both solutions give approximate values. From the fact that the thermal buck­ ling of rectangular plate simply supported b}^ the web is mainly due to the restriction of expanding plate by the web of lower temperature than the plate, and that even if the web is weak and the buckling* is due mainly to the nonuniformity of the tempera­ ture distribution in the plate, such distribution may not happen in such a weak web or, in other words, a weak-heat-sink struc­ ture; the author's solution may be suitable in the case of buckling of supersonic wing panels. In the example calculated, the buckling parameter of the author's solution is somewhat lower than the Klosner-Forray value.