It has become important recently to determine the maximum strength of various structures which have initial deformation caused by fabrication. On stiffened circular cylindrical shell as one of those cases, the authors carried out a study on 2-stage buckling where the shell panels between the stiffeners buckle at first, to be followed by buckling of the stiffeners. For this purpose, the characteristic equations of elastic buckling were formulated under compression and pure bending load considering the reinforced members discretely. The buckling load of stiffeners, after the panel has buckled, was determined by iterative computation on the framework model. The compressive buckling experiments were carried out on three small and two large models with different arrangement of the rings, and the pure bending buckling experiments on a small model. As a result of the experiments, it was found the buckling loads of stiffeners were almost equal to the buckling loads of the panel and the effects of arrangement of rings on stiffener buckling loads were negligible. The experimental value of buckling loads of stiffener has fallen about 25% in the case of compressed buckling and about 19% in the case of pure bending buckling because of initial deformation and torsional deformation of stiffeners. In conclusion, the authors can say that the stiffened cylindrical shells which have similar configuration as these models, have appropriate buckling strength if the allowable load are taken to be equal to the buckling load of panel.