A two-level decentralized control structure is formulated for large scale interconnected subsystems controlled by

decision makers. Chained aggregation is used to decompose the overall team problem with a decentralized information structure into (

) subproblems: one low order team problem with a centralized information structure and

decentralized optimal control problems. Accordingly, the control of each decision maker is decomposed into three components: a decoupling control which induces aggregation, a local control which controls the subsystem dynamics, and an aggregate control which controls the dynamics of the interconnection variables. The robustness of this composite control with respect to perturbations in the system dynamics and the cost functional is established.