Electromagnetic radiation problems involving electrically large radiators and reflectors are solved using the fast multipole method (FMM). The FMM enables the solution of large problems with existing computational resources by reducing the computational complexity by a faster equivalent of O(N) complexity in each iteration of an iterative scheme. Three dimensional radiation problems involving complicated geometries are modeled using arbitrary surface triangulations. Piecewise linear basis functions defined on triangular domains due to Rao, Wilton, and Glisson (RWG) basis functions are used to approximate the induced currents. Using delta-gap voltage sources and prescribed current distributions, the operations of various antennas are simulated.