This paper considers a unified problem of short-term operation planning and power exchange scheduling of large hydro-thermal power systems including: unit commitment, hydro power plant operation planning, pumped-storage hydro power plant operation planning and scheduling of power exchange with other power utilities. The criterion function is the total variable profit incurred by energy production, sales of energy to the users inside the power system, sales of energy to other power companies and purchase of energy from them, or from other sources. The overall problem is solved using the Lagrangian relaxation method. A decomposition technique is applied to solve the dual (mixed-integer) and primal (continuous programming) problem. Dynamic programming, feasible direction method and linear programming method are used for the solution of subproblems. The results of the application of the method to a numerical example are given. >