IN PERIODONTICS there is a need for objective measurements in monitoring disease processes and in assessing the effectiveness of treatment. The purpose of this study was to compare gingival temperatures with indicators of gingival inflammation in order to examine the application of temperature as a diagnostic aid. In six patients the temperature of interproximal sulcular tissue was measured and compared with bleeding upon probing, crevicular fluid flow, pocket depth, plaque accumulation and calculus formation. The results show significantly higher temperatures with bleeding upon probing and with the presence of dental plaque and calculus. Temperature increase correlated with increase in crevicular fluid flow, but a relationship to pocket depth is not clear. The thermocouple microprobe is a very sensitive instrument. The method used is noninvasive, safe and efficient. It can be concluded from our data that differences in gingival temperature reflect not only a regional tissue variability but also can indicate an inflammatory state.