This paper summarizes the study of the applicability of optimal control theories to the design of a pressure regulator for an axial piston pump for which state estimation and advanced control laws can be computed. Considerations are presented for the application of linear optimal control techniques where a weighted, quadratic performance index is minimized. The straight linear optimal regulator was augmented by the first integral of the output pressure to make the system sufficiently robust and to yield a controller that offsets constant or slowly varying flow disturbances. The paper describes the dynamic properties of the pump and their relationships to the available control resources in the form of state's peak values and the power required. Variations in root locations and state peak values for step response of the optimally controlled pump as a function of variations in performance indices are presented and used as a design tool. In addition, pressure responses to a step in flow disturbance for various operating points were studied and presented. The main conclusion drawn is that there will be many engineering situations for which linear optimal control will provide better solutions than will classical design.