Infra-red colour thermography has been used to visualize skin temperatures in two athletes standing and running in an outdoor environment at 20 degrees C and in a climatic chamber at 11 degrees C. Temperature distributions and changes have been recorded on film and analysed. Mean skin temperatures determined by this method have been compared with skin temperatures obtained with a probe thermocouple. During running, skin temperatures were higher over muscles than over other structures and the distribution differed dramatically from that observed before exercise. Regional mean skin temperatures obtained by thermography differed by up to 4 degrees C from those obtained with the thermocouple probe. Overall mean skin temperatures obtained by both methods agreed to within 1-5 degrees C.