The failure to diagnose hypothermic and hyperthermic states can have profound clinical implications. Thus, accurately determining body temperature is an integral component of the evaluation of all emergency department (ED) patients. Oral measurements are most commonly obtained but may not reflect core temperatures. Rectal temperatures are considered more reliable but may not reflect fluctuating core temperatures, and are dependent on site placement. The objective of this study was to determine the practicality and comparative accuracy of tympanic thermographic measurements in the ED. Oral, rectal and tympanic readings were compared in 411 patients. There were significant differences when comparing tympanic to oral (R2 = 0.599, P = 0.0001) and rectal to oral (R2 = 0.554, P = 0.0001) temperatures. In contrast, the correlation between tympanic and rectal measurements was R2 = 0.805, with no significant difference between the two, (P = 0.7077). No complications associated with the use of the tympanic probe were detected. Infrared tympanic thermography is an efficient and noninvasive technique for accurately measuring the temperature of ED patients.