Mixtures of (30:15:55 v/v) CH4-O-2-N-2 or ones diluted with N-2 were converted 20 h in a small- (BaO/CaO catalyst vol. 5 cm(3), 700-800degreesC, 600 W or rarely 1200 or 2400 h(-1)) or a large-scale (Na2O/CaO or BaO/CaO 160 cm(3), 700degreesC, 600 h(-1)) OCM process and bed temperatures were followed. At 55-80 vol.% N-2, hot spots were increasingly flattened, bed temp. was lowered, with neither conversion nor selectivity affected. At 80-95 vol. % N-2, C2H4 and CO2 were formed resp. less and more selectively. The OCM reaction run fast and was completed already in the initial part of the bed. Rather than by reactant concentration and max. temp., the conversion appears to have been controlled by the available O-2 (O-2/CH4 kept fixed at 0.5). The inert gas acted quite similarly as did the catalyst bed solid diluent examined before.