This study investigates limits of implicit disturbance rejection capacity of negative feedback control systems on the basis of communication channel limitations. Disturbance rejection performance of closed loop control structure is evaluated by using reference to disturbance ratio (RDR). Boundaries of RDR performance for stable control system are investigated by using stability boundary locus analyses. For computer-aided system design problems, a graphical design method for disturbance rejection PID control system is presented and illustrative examples are shown. Numerical examples show that disturbance rejection control with improved step response performance is obtainable by two-degree-of-freedom design combining high gain PID control and input prefiltering.