This paper deals with a contact stress distribution in bolted joints when a full face metallic flat gasket is interposed between two pipe flanges. Replacing a gasket and pipe flanges by finite hollow cylinders the contact stress distribution is analyzed using three-dimensional theory of elasticity. By numerical computations, effects of the thickness and the stiffness of gaskets on the contact stress distribution are shown. Next, the force ratio of bolted joints with gaskets, which is the ratio of an increment of bolt axial force to an internal pressure and the sealing performance are analyzed. With an application of the internal pressure, a bending moment is produced in bolts. The maximum stress produced in bolts taking this bending moment into consideration is also analyzed. For verification, experiments are performed. Analytical results are in a fairly good agreement with experimental one.