Oxygen electrodes were tested for response to variables in construction, assembly, and use. The half-wave potential was found to be inversely proportional to the KOH concentration used in assembling the electrode. The half-wave potential was moved to higher voltages by the use of thin membranes and by the use of Teflon rather than polyethylene membranes. This potential was not affected by cathode size, aging of the electrode, temperature, or replacement by carbonate of the hydroxide behind the membrane. Stirring effects can be reduced by low temperature, thick membranes, and small cathodes. Response time is the same for polyethylene and Teflon membranes and is proportional to the square of membrane thickness. Electrode blank, stability, and zero oxygen error are all discussed. The use of Teflon membranes, 1 n KOH as electrolyte, and 1.1-v polarization voltage is recommended. voltage plateau; Teflon membrane; respirometry; polarographic oxygen eletrode Submitted on September 14, 1964