The use of infrared tympanic thermometry has become a common method of measuring body temperature in Norwegian hospitals. This report summarizes the documentation of diagnostic accuracy of infrared tympanic thermometry compared to rectal thermometry to identify fever among adult patients in hospital or in nursing homes. In addition we have searched for studies that compare oral, axillary and temporal thermometry with rectal thermometry. The review shows that the diagnostic accuracy of tympanic thermometry compared to rectal thermometry is sparsely documented. We identified eleven small cross-sectional studies (N=1426). Most studies evaluated tympanic thermometry, some evaluated oral or axillary thermometry. No studies evaluated temporal thermometry. Correct and observer-independent use of infrared tympanic thermometry can be challenging in a clinical setting. Comparing temperature measurements of different body sites might also be problematic, because the measurements at different sites are all estimates for what we wish to know, the core temperature. Although rectal measurements are considered as reference standard in this review, we acknowledge that this is imperfect in many ways. The studies showed that in general, infrared tympanic thermometry did not identify an acceptable part of patients with fever detected by rectal thermometry (low sensitivity). Infrared tympanic thermometry resulted in few false positive readings (high specificity). Since the studies included few patients with fever measured rectally and had different cut offs for fever, the sensitivity values are uncertain. Given the widespread use of infrared tympanic thermometers, further documentation of diagnostic accuracy and repeatability of newer models used in a clinical setting is needed.