Two new theoretical results about interpolated controllers for the transition control and simultaneous stabilization of single input-single output plants with variable operating conditions are shown; recent results are generalized for interpolated controllers. On the basis of these results, an application to the closed-loop transition control of a continuous stirred-tank reactor, where a single exothermic reaction takes place, is presented A comparison with simple PI controllers is made. (c) 2005 American Institute of Chemical Engineers.