Adjoint optimization methods have proven successful for the control of turbulence and boundary layers and in the design of airfoils and aircraft. We present results from applying the adjoint methodology to the problem of controlling steady supersonic flow with volumetric source terms in the Euler equations, i.e. mass, momentum and energy addition. The resulting analysis yields not only the optimal location for source placement but also the benefit-to-cost ratio as a function of source location and intensity. The very general formulation of the problem makes these results applicable to many forms of volumetric flow control with the goals of drag reduction, lift enhancement and the generation of turning moments.