General principles of thermoregulation, the pathophysiology of fever, controversies concerning the use of antipyretic therapy, and nonpharmacologic and pharmacologic treatments commonly used for antipyresis in the pediatric population are reviewed. Several arguments can be made for not ameliorating the febrile response. Fever is an important diagnostic and prognostic clinical sign that may have beneficial effects for the host. In addition, body temperatures of < or = 41 degrees C (105.8 degrees F) are relatively harmless. Reasons for treating fever include patient discomfort, the potential for adverse sequelae, the possibility of seizures, and the possibility that fever could affect the pharmacokinetic profiles of drugs. Nonpharmacologic treatment for fever includes environmental measures to enhance dissipation of body heat and sponging. Aspirin and acetaminophen are the agents used most frequently for antipyresis in pediatric patients. However, aspirin use in children with a viral illness has been associated with development of Reye's syndrome. As a result, its use in children has declined in the United States. Acetaminophen is relatively free of adverse effects and is considered first-line pharmacologic antipyresis therapy. Ibuprofen suspension should be considered as second-line antipyretic therapy. Combination therapy with acetaminophen and aspirin may be considered if the patient fails to respond to other nonpharmacologic and pharmacologic therapies; however, combination therapy may result in increased risk of drug toxicity, increased probability of adverse reactions, and increased risk of intoxication. Aspirin, acetaminophen, and ibuprofen are equally effective for antipyresis in pediatric patients. However, because acetaminophen is the safest medication, it is currently the therapy of choice.