We present a novel dual thin-layer flow cell double-disk electrode design, which due to its high collection efficiency in combination with a reasonable time resolution allows highly sensitive measurements of electro-active species generated during electrochemical reactions on the working electrode. Most important, it allows for rapid changes of the electrolyte during the measurements, which in combination with a thin-film electrode, where an inert glassy carbon substrate is covered by a thin film of carbon-supported noble metal catalyst, makes it particularly useful for kinetic studies on electrocatalytic fuel cell reactions under realistic conditions (continuous reaction, continuous electrolyte flow) and on realistic materials (supported catalysts).The performance of the set-up and its suitability for kinetic studies, in particular for transient experiments involving rapid electrolyte exchange, are demonstrated in potentiodynamic and transient potentiostatic measurements for the oxygen reduction reaction on carbon-supported Pt catalysts and, for comparison, on Pt-free Vulcan carbon supports. (C) 2003 Elsevier Ltd. All rights reserved.