Two methods for the estn. of the current bypass in solid state electrochem. are presented. The current bypass was estd. from the current-voltage curves of a tubular cell with one bipolar element and from the current-voltage curves of a monolith with several bipolar elements. A current bypass of 11.5% was found in the tubular cell and a current bypass of 34% in the monolithic configuration, both at high cell voltages. The current bypass in the tubular cell is almost independent on the applied current between 500 and 1000 mA. The current bypass did not show an important influence on the electrochem. promotion. A much more important influence was found due to the bipolar polarization of the catalyst. The nonuniform distribution of the work function led to a smaller increase of the ethylene conversion during the bipolar polarization than during the direct anodic polarization. [on SciFinder (R)]