Body temperature is a balance of the hypothalamic set point, neurotransmitter action, generation of body heat, and dissipation of heat. Drugs affect body temperature by different mechanisms. Antipyretics lower body temperature when the body’s thermoregulatory set point has been raised by endogenous or exogenous pyrogens. The use of antipyretics may be unnecessary or may interfere with the body’s resistance to infection, mask an important sign of illness, or cause adverse drug effects. Drugs may cause increased body temperature in five ways: altered thermoregulatory mechanisms, drug administration-related fever, fever from the pharmacologic action of the drug, idiosyncratic reactions, and hypersensitivity reactions. Certain drugs cause hypothermia by depression of the thermoregulatory set point or prevention of heat conservation. By affecting the balance of thermoregulatory neurotransmitters, drugs may prevent the signs and symptoms of hot flashes.