In the first part an account is given of the methods, tried in the Laboratory of Physical Chemistry, Upsala, for measuring the speed of the ultracentrifuge. The methods can be classified according to the nature of the primary indicator, which may be of optical or of electrical design. In the first case (optical methods) the stroboscope and a photo‐cell device are considered. In the second case an electrical indicator of the following type has been designed and constructed. A part of the rotor shaft has been magnetized in a radial direction and a stator is mounted in the centrifuge casing. The frequency or the e.m.f. of the power produced by the indicating generator is measured by means of different methods. The oscillograph, different resonance circuits and bridge circuits have been considered. In the second part a description is given of a device for the automatic regulation of the speed of the ultracentrifuge. The frequency from the indicating generator is connected to a bridge. The output voltage from this is applied to a phase reversing bridge, which controls the oil supply to the centrifuge turbines by means of relays.