An investigation of the spatial decomposition technique (SDT) for the analysis of electrically large objects is presented. We apply SDT to two-dimensional perfectly conducting cylinders under TM excitation. Some of the convergence issues of the SDT as well as its application to finite arrays (finite frequency selective surfaces) are discussed. We also present a new method to obtain a reduction in the operation count of SDT, which is referred to as "reduced current fidelity (RCF)." With RCF the coupling between distant SDT subobjects is determined by use of a coarse grid on which currents are obtained from those on a dense grid. An averaging of the currents on distant objects reduces the operation count involved in determining the coupling to other subobjects. It is shown that for electrically large structures, RCF can provide significant reduction in operation count and good accuracy in the resulting structure currents.