A system for measuring the friction surface temperature in disc clutches was developed. This system measures the transient surface temperature on rotating clutch discs by infrared detection. The temperature distribution on the friction surface can be obtained. The computer in the system records the temperature signals and processes them into color contour maps representing temperature distributions. Experiments were made in which the friction surface temperatures on a wet friction clutch disc were measured at various engagement speeds and forces. The experimental results showed that under the conditions used the friction surface temperature was so non-homogeneous that the temperature difference could be as much as 200°C at a moment in engagements. It was also found that the high temperature was concentrated on a narrow belt of friction surface in engagements. Tests were made only on the sintered-bronze-lined friction discs.