This paper investigates the problem of improving the output step response obtainable with PID controllers. The solution proposed is based on a supervisory switching control. First, a family of candidate stabilizing conventional PID regulators are designed on the basis of a suitable plant model. For each controller the corresponding feedback connection with a plant model is defined and the resultant output prediction error is used to form a real, positive definite functional giving a measure of the future controller performance. At any time instant, the supervisor exploits these measures for on-line selecting the most appropriate controller to be connected to the plant at the same time instant. The stability of the control system is guaranteed by the introduction of a suitably defined dwell time into the switching logic.