A device is described which permits the measurement of rotor temperature in the air‐driven ultracentrifuge while the machine is in operation at speeds up to 60,000 r.p.m. A Thermistor situated inside the rotor changes its resistance as the temperature changes. Measurement of the Thermistor resistance by means of a Wheatstone bridge is accomplished with the use of needle contacts on the top of the turbine shaft and at the bottom of the rotor. Rotor temperature may be measured to within ±0.02°C and is believed to represent actual temperature of the rotating solution within 0.1°C.