This study aims to continuously measure nasal mucosal temperature without interruption of nasal breathing using infrared thermometry. An infrared thermometer (Medi-Therm 310; Everest Interscience, Inc.) was directed at the nasal septum from a distance of 15 cm. Infrared radiation was continuously collected, then converted to an electrical signal proportional to the mucosal temperature and output to a chart recorder. In 70 subjects the mean nasal mucosal temperature was 30.4 +/- 2.0 degrees C on inspiration and 32.0 +/- 1.8 degrees C on expiration. Using multiple regression, nasal mucosal temperature was significantly related to atmospheric temperature (p < 0.0001) and inversely related to the airway patency of the ipsilateral nasal passage (p < 0.05).