Our objective was to determine the most reliable site for temperature measurement in children. In anesthetized children esophageal temperature readings were closest to those in the pulmonary artery (mean difference 0.1 degree C +/- 0.5 degree C compared with Genius tympanic thermometer (mean difference 0.6 degree C +/- 1.0 degree C), IVAC tympanic thermometer (mean difference 0.8 degree C +/- 1.0 degree C), rectal probe (mean difference 0.7 degree C +/- 1.7 degrees C), bladder probe (mean difference 0.9 degree C +/- 1.4 degrees C), and axillary probe (mean difference 1.3 degrees C +/- 1.3 degrees C).