Critical rotational speeds and redistributed stresses are determined for polar orthotropic rotating annular disk of variable thickness considering the actual centrifugal force in which radial displacement is included. In the classical analysis of the rotating disks, the centrifugal force expression does not include the radial displacement, and instability has not been observed in the results. The effect of various parameters on the instability of disk is investigated and results are tabulated. The redistributed stresses versus critical rotational speed are also depicted. The solutions obtained analytically are in terms of non-dimensional parameters.