Two-level, hierarchical, partially decentralized control is considered for a large-scale system composed ofMlinear static subsystems with an interaction and a quadratic performance index. The coordinator and the local controllers, using their different information, realize the control resulting from the global and local optimization, respectively. It is seen that the optimal control laws are linear functions of some estimates and are determined by the formulated two-level certainty equivalence principle. A discussion on the usefulness of the application of particular local controllers is described.