The definition of normal body temperature as 37°C still is considered the norm worldwide, but in practice there is a widespread confusion of the evaluation of body temperature, especially in elderly individuals. In this paper, we discuss the relevance of normal body temperature as 37°C and consequences in clinical practice. Our conclusion is that body temperature should be evaluated in relation to the individual variability and that the best approach is to use the same site, and an unadjusted mode without adjustments to other sites. If the baseline value is not known, it is important to notice that frail elderly individuals are at risk of a low body temperature. In addition, what should be regarded as fever is closely related to what is considered as normal body temperature. That is, as normal body temperature shows individual variations, it is reasonable that the same should hold true for the febrile range.