The analysis of vibratory and acoustical signals from rotating machinery has been used successfully for several decades to determine the adequacy of rotating machine design or operation. Certain vibration or acoustical signals are characteristic of machines encountering problems or near failure. Likewise the thermal signature from a rotating machine may have significant diagnostic value. Friction, damping and material deformations are typical sources of thermal energy easily detected by thermal measurements. Thermocouple thermography has been used to determine rotating machine temperatures. However, point measurements are difficult to obtain because of signal coupling problems with the rotating machine. In the past temperatures could only be obtained by stopping the machine and quickly taking temperature measurements hoping that the temperature information would not dissipate by transient affects. Infrared thermography has solved some of these problems by offering a noncontact thermal measurement along with a display of. temperature fields which facilitates the location of hot spots. Several examples of rotating machinery are reviewed such as couplings, power transmission belts, gears and rotors. The significance of the temperature distribution on the power transmission component is discussed. Infrared thermography appears to be a useful tool in diagnosing problems in rotating machinery.