A gas bubble chamber was used to study the prebreakdown mechanism in diethyl ether. The liquid was saturated with CO2gas at a pressure of 9–13 kg/cm2and then further compressed to a pressure of 40–45 kg/cm2. The liquid was then rapidly expanded 4–6% in volume, causing it to become temporarily supersaturated. At that time an impulse voltage of about 33 kV/was applied between two needle electrodes (gap length 3.2 mm) in the liquid. The resultant bubble figures, which represent electron emission from the cathode, were recorded photographically. The time lag from the application of the impulse voltage to the growth of bubbles of observable size was about 0.8–1.0 msec. This value agrees with the results obtained by using an ordinary bubble chamber.