This study was conducted to quantitate the degree of inflammation associated with oral lesions by using infrared thermography. It was reasoned that the increased vascularity associated with inflamed tissue may result in measurable increases in surface temperature. One subject with normal oral mucosa and three subjects with oral lesions of varying causes were studied with a thermal video system, using an infrared imager and microprocessor. A clinical photograph of each subject was obtained. Multiple thermograms were made in a temperature range of 30.0 C to 34.2 C at a sensitivity of 0.2 C. Photographs were taken on different occasions to determine whether the temperature readings could be duplicated and to test the accuracy of each reading. The normal surface temperature of the control subject's mucosa was significantly cooler than were the temperatures of the inflamed areas in the subjects with lesions induced by chemotherapy. The temperature of the areas of stomatitis was consistent (subject 3, mean = 33.7 C; subject 4, mean = 33.9 C). The necrotic center of a traumatic ulcer inhibited measurement of an underlying inflamed base and, thus, was equivalent to the control in temperature (subject 1 (control), mean = 31.9 C; subject 2 (necrotic lesion), mean = 31.7 C). These results suggest that infrared thermography may provide a means to quantitatively assess the degree of mucosal inflammation.