Title: Efficient Spectral-Galerkin Methods III. Polar and Cylindrical Geometries Author: Jie Shen Status: SIAM J. Sci. Comput. Vol. 18, No. 6, 1997 Abstract: We present in this paper several extremely efficient and accurate spectral-Galerkin methods for second- and fourth-order equations in polar and cylindrical geometries. These methods are based on appropriate variational formulations which incorporate naturally the pole condition(s). In particular, the computational complexities of the Chebyshev-Galerkin method in a disk and of the Chebyshev-Legendre Galerkin method in a disk or a cylinder are quasi-optimal (optimal up to a logarithmic term). As an indication of efficiency, the CPU time for the Poisson solver on a disk by our Chebyshev-Galerkin method is only about 70\% of the corresponding finite-difference code in FISHPACK.