This paper describes some recent studios that have been carried out on the hierarchical feedback control of largo interconnected dynamical systems. Methods are outlined for solving both large linear quadratic and non-linear problems. It is found that for the linear quadratic case it is possible to obtain a feedback control which is independent of all initial condition disturbances. This is demonstrated ona22ud-order river pollution control problem. For the nonlinear case, the control is however dependent on the initial conditions, although experience suggests that this dependence is in fact quite weak. This is shown on a highly non-linear example of two coupled synchronous machines where the same control law is able to provide near-optimal performances for varying initial conditions.