Clinical measurements such as temperature are commonly used for screening and diagnosis. However, little is known about the reliability of specific thermometers or measurement techniques.This study sought to define normal tympanic temperature and to assess the reliability of tympanic thermometry. Using a cross-sectional survey design, 244 children aged between one and six years at a paediatric outpatients department had their temperature recorded three times in each ear using a Braun Thermoscan thermometer.Mean temperature was 36.65 degrees C with an overall repeatability statistic of 0.78 degrees C, 0.55 degrees C in the left ear and 0.64 degrees C in the right. The level of measurement error did not increase with temperature, or differ between ages. Environmental temperature had only a moderate effect on temperature, and there was no effect from environmental humidity.Tympanic thermometry using the Braun ThermoScan is a reliable method of temperature measurement, with a temperature change of approximately 0.6 degrees C being significant. Although the effects of environmental conditions were slight, these were in temperate conditions. This study should be repeated for other models of thermometer.