The dynamic stiffness method has been applied to the evaluation of the natural frequencies of rotating systems. To this purpose, a rotating “Rayleigh beam,” defined by adding the effect of the rotary inertia and the gyroscopic effects to the Bernoulli-Eider beam, has been formulated and its dynamic stiffness matrix is presented in this paper. The effects due to the presence of concentrated disks, as well as of elastic, isotropic supports, have been included in the formulation. The usual matrix assembly procedure is used in order to obtain the global dynamic stiffness matrix of the system. The natural frequencies of the system are determined by utilizing an iterative root searching technique. Numerical results, obtained for a rotor system taken from the literature on this subject, are presented.Presented at the 45th Annual Meeting in Denver, Colorado May 7–10, 1990