Fever, or pyrexia, is an elevation of body temperature above the normal range. Fever is most commonly defined as a body temperature greater than 38 °C; however, the defining criteria may differ among individuals. Fever is a complex physiological response most commonly associated with infectious causes (bacterial or viral infections) but may also be caused by noninfectious diseases such as immune-mediated or inflammatory diseases, drug causes, or malignancies. Fever is a normal immune response that is rarely harmful and often does not require treatment with medications. Assessment of patients presenting with a fever requires knowledge of the variations in temperature among individuals and among different sites of measurement of body temperature. Assessment of the history and characteristics of a fever and the presence of any associated symptoms is essential. It is important to determine if any red flags are present, as they could be indicative of a serious bacterial infection or adverse drug reaction, which can be life-threatening. Pharmacists play an important role in the assessment of patients with fever. By obtaining a focused clinical history from the patient, they can identify patients who need to be referred to their physician or to the emergency room, as well as which patients can be managed at home. Pharmacists should also be aware of some of the challenges of medication use in children and the various antipyretic formulations available.