A new method is described by which a plated quartz crystal oscillator is used for the measurement of sputtering. The crystal is placed in a molecular beam and sputtering of its plating is measured by the frequency change of the oscillator. The relationship between the frequency change of the oscillator and the change in plating mass of the crystal is given. The method is extremely sensitive. Sputtering of less than a millimicrogram of plating can be measured. A wide range of material can be used to plate the crystal. A crystal oscillator sputtering gauge was built by using a frequency counter with a digital readout to record the oscillator frequency. The operation of the gauge is illustrated by preliminary measurements on the sputtering rates of gold in an argon beam between 0 and 100 ev. Other uses of the gauge, such as a neutral beam detector, are also discussed.