An apparatus is described for the measurement of the low‐frequency (0.0003 to 2 cps) dynamic properties of solid and liquid polymers. It is basically a torsion pendulum driven in forced vibration by a low‐frequency sinusoidal current. The current generator, which is a mechanically‐driven potentiometer arrangement, is also briefly described. The treatment of data, calibration, and areas of usefulness of the instrument are discussed, and an example of the results of its application to a concentrated polymer solution is given.