The dynamic stability of radially stiffened annualar plates with both edges subjected to in-plane forces is studied. For this purpose a sector and a beam finite element is used. The method is applied to annular plates with several stiffeners of uniform rectangular cross-section located at equal angular intervals. The instability regions are determined for a wide range of exciting frequencies with different boundary conditions using Bolotin's method by varying the number and size of the stiffeners. Also the effect of static forces are taken into account.