10.1542/6278331392001 Video Abstract PEDS-VA_2021-053412 6278331392001 OBJECTIVES To determine the (1) frequency and visit characteristics of routine temperature measurement and (2) rates of interventions by temperature measurement practice and the probability of incidental fever detection. METHODS In this retrospective cohort study, we analyzed well-child visits between 2014–2019. We performed multivariable regression to characterize visits associated with routine temperature measurement and conducted generalized estimating equations regression to determine adjusted rates of interventions (antibiotic prescription, and diagnostic testing) and vaccine deferral by temperature measurement and fever status, clustered by clinic and patient. Through dual independent chart review, fever (≥100.4°F) was categorized as probable, possible, or unlikely to be incidentally detected. RESULTS Temperature measurement occurred at 155 527 of 274 351 (58.9%) well-child visits. Of 24 clinics, 16 measured temperature at >90% of visits (“routine measurement clinics”) and 8 at <20% of visits (“occasional measurement clinics”). After adjusting for age, ethnicity, race, and insurance, antibiotic prescription was more common (adjusted odds ratio: 1.21; 95% CI 1.13–1.29), whereas diagnostic testing was less common (adjusted odds ratio: 0.76; 95% CI 0.71–0.82) at routine measurement clinics. Fever was detected at 270 of 155 527 (0.2%) routine measurement clinic visits, 47 (17.4%) of which were classified as probable incidental fever. Antibiotic prescription and diagnostic testing were more common at visits with probable incidental fever than without fever (7.4% vs 1.7%; 14.8% vs 1.2%; P < .001), and vaccines were deferred at 50% such visits. CONCLUSIONS Temperature measurement occurs at more than one-half of well-child visits and is a clinic-driven practice. Given the impact on subsequent interventions and vaccine deferral, the harm–benefit profile of this practice warrants consideration.