A method has been devised for accurate determination of the absolute rate of sputtering, i.e., the measurement of the number of atoms liberated from a metallic target under the impact of a single ion of known energy. The accuracy of this measurement was 6 to 7 percent—a precision hereto unattainable by other methods. The apparatus producing argon ions consisted of a strong ion‐source of capillary‐arc type. The ions were accelerated within a high vacuum chamber through a potential, which was varied from 2000 to 7000 volts, and then allowed to strike a metallic target. The sputtering rate was determined by measuring the positive ion current to the target and the loss of target material. Results are given on sputtering of silver by argon, and on the secondary electron emission from aluminum and molybdenum.