Background: Tympanic membrane temperature is often used as a reliable indicator of core temperature. In practice, temperature measurement in one ear is considered adequate for clinical decision-making in the postoperative phase. If one ear tympanic membrane temperature is found to be abnormal, the other side is checked and the higher reading is used. The authors tested the scientific validity of this practice. Methods: Both ear temperatures were measured within a few seconds of each other among a convenient sample of patients in the postoperative recovery unit. Measurements were alternated between the left and right ear in consecutive patients to avoid bias. Results: A total of 300 patients were recruited (136 male, 45.3%) with a median age of 47.2 years (range 10.6–94.4 years). The mean temperature in the left ear was 36.53°C (SD 0.63) and in the right 36.57°C (SD 0.62). The temperature difference between the two ears was not significant and did not correlate with body weight (p=0.2), age (p=0.09) or duration of surgery (p=0.3). In addition, 16.9% of patients were hypothermic (<36.0°C) on arrival in the recovery room and were significantly older than the non-hypothermic group (p=0.03). Discussion: The temperature difference between the two ears post-surgery was less than 0.5°C among 90% of subjects and was not statistically significant. Therefore, routine temperature measurement in one ear seems clinically acceptable practice.