This talk presents a review of numerical techniques for modeling of microwave circuits and antennas. Then, it introduces EMPiCASSO, a powerful electromagnectic CAD tool that provides an integrated environment for analysis, synthesis and optimization of multilayer printed microwave circuits and antennas. EMPiCASSO has been built on an object-oriented foundation that allows a systematic integration of all preprocessing, processing and post-processing tasks within a single unified visual interface. The integration of the moment method (MoM) simulator, network simulator and a new finite element (FEM) simulator are discussed, and examples will be presented for hybrid MoM/FEM simulation of complex structures. The talk will continue with a discussion of parallelization of the simulation codes on high performance computing resources. Results will be presented on the scalability of the MoM and FEM codes for some large-scale electromagnetic problems involving thousands to millions of unkowns. The talk will conclude with a live demonstration of EMPiCASSO.