The purpose of the present paper is to illustrate the use of the Compton Quadrant Electrometer for current measurement by the rate of deflection method. There are several points in the theory and technique for this instrument which do not appear to have been mentioned in any previous papers. With the Compton Electrometer the rate of deflection method gives accurate measurements of currents of 10−14 amperes in less than a minute. The instrument is of course more difficult to use than the Dolezalek type, and it is for this reason that an attempt is made here to discuss and illustrate its use. The theory is given in Compton's original paper and there is also an important note on the subject by Cox and Grindley.