In this paper, exergonomic theory is applied to an air-conditioning system for optimization purposes. The investigation is addressed to an all-air system with air recirculation. The thermodynamic cycle includes a mixing plenum, a cooling and heating coil, chiller, and heater. The thermodynamic model is stated according to recent formulations of exergy for moist air streams, while the economic model is based on cost balance equations and real cost data for mechanical equipment. The objective function to minimize includes the following decision variables: fresh to total air rate, coefficient of performance for the chiller, inlet temperature of water for the cooling and the heating coils, temperature difference of the same streams. For the exergonomic optimization, the authors followed the approach proposed by Tsatsaronis (1984). The optimum configuration is obtained through an iterative procedure aimed at the design improvement. The results show that there is considerable room for improvement with respect to a system based on typical design parameters.