A theoretical analysis on the radiation pattern and the radiation resistance of an annular ring microstrip antenna mounted on a spherical body using an electric surface current model is presented. The effects of the dielectric layer and the metallic sphere are rigorously taken into account by the Green's functions in the spectral domain. Results for the antenna operating in the TM01 (wraparound antenna) and TM12 modes are given. © 1994 John Wiley & Sons, Inc.