This study investigates the vibration characteristics of spinning annular disks with various boundary conditions aiming to investigate the effect of radius ratio parameter and the rotation speed on natural frequencies of a spinning disk analytically for nine different types of boundary conditions. The stress distributions on the disks are obtained for all boundary conditions. The Galerkin method is employed with polynomial functions as approximate displacement functions. Analytical results are presented and compared to the results of the finite element analyses as well as experimental ones.