A finite element procedure has been used for the analysis of the vibrations of thick, polar orthotropic annular disks. Mindlin's thick plate theory, including transverse shear deformation and rotatory inertia, was used. The effects of transverse shear deformation and rotatory inertia on the frequencies of disks subjected to various boundary conditions have been compared. Natural frequencies of disks with the inner edge clamped and the outer edge free have been studied in detail. A few frequencies of disks subjected to other boundary conditions have also been presented. Some conclusions have been drawn from the trends observed. © 1991.