We describe a multiple wall-jet flow cell setup for parallel evaluation of the electrocatalytic activity of carbon-supported electrocatalysts under relevant reaction conditions (i.e., under enforced and controlled mass transport and at elevated temperatures). The performance of the setup is illustrated using the oxygen reduction reaction (ORR) as a test reaction and a four-cell setup for demonstration. The identical current voltage characteristics obtained on four equally prepared Pt/C thin-film electrodes at reaction temperatures between 30 and 80 degrees C demonstrate (i) similar flow conditions in the different cells, as evidenced by the same mass transport limited ORR currents, (ii) a high-temperature stability, and (iii) a high reproducibility of the measurements and in the fabrication of the thin-film electrodes. Parallel multiple-cell measurements and (sequential) measurements in a single-cell setup, using a set of four different commercial (E-TEK, Inc.) carbon-supported catalysts (Pt/C, PtCo/C, PtCr/C, and Pt3Cr/C), result in similar reaction kinetics in both setups. The potential of the setup for parallel catalyst screening under fuel cell relevant reaction conditions is discussed. (C) 2008 The Electrochemical Society.