Recently stress analysis of hull structure of tankers using electronic computer has been utilized widely, and we can get more accurate information about the stress distribution in transverse and longitudinal members under various loading conditions. There are, however, some problems in calculating the stresses at the bilge part which is considered to be one of the most important part in transverse strength. One of the problems is that the effectiveness of face plate and skin plate and it has not been made clear sufficiently. In general, face plates are fit with brackets and skin plates are reinforced by longitudinal stiffeners, but the effect of these members on efficiency of face plates and skin plates is also obscure. Experiments are made to investigate these problems, and the following conclusions are obtained. 1) The effectiveness of skin plate at bilge part is very small, and longitudinal stiffeners have not so large effect to efficiency of skin plate in the case that the usual number of stiffeners are attached. 2) Brackets have a little effect to efficiency of a face plate, but it is considerably effective to adopt a thick and narrow face plate. 3) The formulas on effectiveness of the shell of stiffened cylindrical shell which had obtained by Tlatirlimann or Anderson can be used as far as the usual type of structure is considered, and another theory must be applied when the number of brackets or longitudinal stiffeners increases