Stray admittance and lead effects may be eliminated from the calibration of a condenser microphone by use of three‐terminal measurement techniques. Modern ac‐bridge null‐balance methods applied to the measurement of electrical transfer impedance between two condenser microphones, cavity coupled for reciprocity calibration, result in a significantly higher accuracy than attainable by currently used deflection‐comparison methods, and yield phase in addition to amplitude information. Using the bridge described reduces the uncertainty arising from all electrical measurements in the reciprocity determination of condenser microphone pressure response to less than ±0.006 dB from 400 Hz to 600 Hz, ±0.004 dB from 600 Hz to 1000 Hz, and ±0.01 dB at 10 kHz.