It is shown how the influence of gravity can be incorporated without difficulty in the previously developed "structural mechanics method"  for the analysis of uniaxial vibration of compressible fluids in piping systems. Two separate effects are treated: (a) a stiffening or weakening of each fluid column depending on its orientation in the gravity field; (b) a linear density variation along each straight member caused by the static compression of the fluid. The required modifications are introduced in the member mobility matrices only. Thus no alterations are needed in the global system assembly described in reference . Rigid body and elastic body vibrations are treated in a unified manner in the present formulation. Five numerical examples demonstrate and verify the method. The gravity effect of type (a) is found to be larger at low frequencies than at high frequencies, and it is of vital importance to include this effect for systems with rigid body degrees of freedom (open systems). Type (b) is shown to be negligible in most practical situations involving only the natural gravity g=9·81 m/s 2.