This paper considers the robust implementation of a class of predictive control methods represented by GPC. Such controllers are in two-degrees-of-freedom form where there are dynamics in both the forward and the feedback paths. The ‘tuning knobs’ of predictive controllers determine the characteristic polynomialPC, and for a givenPCthe observer or prefiltering polynomialTin the feedback path determines the robustness of the closed loop. Previous intuitive guidelines on the selection ofTare shown to be limited in their effectiveness. For an open-loop stable plant, a simple criterion is provided which allows the feedback dynamics to be specified so as to enhance robustness. TheTpolynomial is then chosen to satisfy this criterion. In addition, robust design throughTis related to anH∞-optimal control scheme using the so-calledQ-parametrization. Despite its simplicity, the new proposed approach to the design ofTis seen to result in robustness comparable with that obtained from theH∞method.