This abstract presents the results obtained by theoretical and experimental methods for the buckling of honeycomb sandwich panels in shear. Details of the specimens analysed are shown in Figs. 1 and 2. The test rig is shown in Fig.3, and the accuracy with which uniform shear was obtained is illustrated in Fig.4. The experimental results are given in Fig. 5, where buckling and failing shear stresses are plotted against the ratio panel width "b" to panel thickness "d". No consistent effect attributable to the difference in face thickness for the panel series A and B is shown by these results. Comparison between theory and experiment is shown in Figs. 6 and 7. The results for buckling agree substantially with plate theory for the case of simply supported edges. Corrections of plate theory to allow for shear flexibility of the filling can virtually be neglected. Discrepancies between theory and experiment for b/d <80 are probably due to an insufficiently accurate allowance for plasticity.