This paper describes the development of a novel laboratory reactor system consisting of two interconnected fluidized beds. This system has been utilized, over the last three years, for the, study of the catalytic oxidation of HCl to chlorine. During operation a stream of HCl in O-2, and N-2, is continuously supplied to one of the fluidized-bed reactors, defined as the "oxidizer," working in the temperature range of 340-400 degrees C. In this reactor HCl is converted to chlorine and water vapor. The exit stream from the oxidizer is then fed into the second reactor, defined as the "chlorinator", operating in the:temperature range of 180-200 degrees C. There, all HCl that was left unreacted in the oxidizer reacts with the catalyst present, thus resulting in a HCl-free chlorinator exit stream. The catalyst in the chlorinator, after reacting with the HCl, is subsequently recirculated into the oxidizer, where it is "regenerated" in the presence of oxygen. The as prepared fresh catalyst consists principally of equimolar amounts of copper and sodium chloride supported on a zeolite carrier, which has good fluidization characteristics. Prior studies by our group had focused on the behavior of each individual reactor, and have helped to develop the dual fluidized-bed reactor system discussed here. Our current study focuses on the behavior of this combined system. Of particular interest was to determine the optimal range of operating conditions, which result in over 99.5% conversion of the HCl to Cl-2,. Reactor parameters that we have investigated in detail include the oxidizer and chlorinator temperatures, the catalyst circulation rate and its residence time in each fluidized bed reactor, the HCl/O-2, ratio in the oxidizer feed, and the fluid velocities in both reactors.