This paper presents a methodology to simultaneously determine the locations and input signals for multiple Static Var Compensators (SVCs) in order to damp multiple electromechanical oscillation modes in extensive power systems. This methodology combines Modal control theory and Multiple Input Multiple Output (MIMO) control theory. Modal control theory indicates the sensitivity of a controller to the critical mode of interest, whilst MIMO control theory gives a measure of interactions caused by decentralized control. The usefulness of this methodology is illustrated on a 46 generator, 190 busbar, 253 circuit test power system.