A vibrating‐sample magnetometer, which measures the magnetic moment of a sample when it is vibratedperpendicularlyto a uniform magnetizing field, is described. With this instrument, changes as small as 10−5to 10−6emu have been detected, and a stability of one part in 104has been attained. In addition to permitting convenient measurements in the usual laboratory electromagnet, this instrument eliminates or minimizes many sources of error found in other methods. It is simple, inexpensive, and versatile, yet permits precision magnetic moment measurements to be made in a uniform magnetizing field as a function of temperature, magnetizing field, and crystallographic orientation. The mechanical design and detailed operating characteristics are presented. Applications and limitations of the method are outlined.