The PI-PD controller structure provides an excellent four-parameter controller for control of integrating, unstable and resonant processes to set point changes while the conventional PID controller has limitations in controlling such systems. In this paper, a graphical method for the computation of all stabilizing PI-PD controllers is given. The proposed method is based on plotting the stability boundary locus, which is a locus dependent on the parameters of the controller and frequency, in the parameter plane. The stability boundary loci are first obtained in the ($K_d$, $K_f$) and ($K_p$, $K_i$) planes and then it is shown that all the stabilizing values of the parameters of a PI-PD controller can be found. Computation of stabilizing PI-PD controllers which achieve user specified gain and phase margins is also studied. The method is used to design robust PI-PD controllers for control systems with parametric uncertainties. A design procedure for interval control systems is proposed. Examples are given to show the benefit of the method presented.