The problem of optimum scheduling of hydro-thermal power systems is considered. A functional analytic optimization technique is applied to a general system. The power system considered contains (n-m) hydro-plants on the same stream. The time delay of the flow between upstream and downstream plants is taken into consideration. This is an extension of the results reported in . Optimal solutions to some special cases of this problem are given and shown to agree with results obtained earlier using other techniques. The resulting optimal schedule can be easily incorporated in existing economy dispatch program that neglect the hydraulic coupling.