Some women report that they have fewer hot flashes when they have a fever. This is the first case of physiological monitoring of hot flashes during fever in a subject with a well documented pattern of frequent hot flashes when afebrile. During fever, there were fewer hot flashes than during afebrile periods, and these hot flashes also tended to be less intense. For most of the period of reduced hot flashes, internal (core) temperature was elevated, above 37.5 degrees C. When the fever broke, hot flashes resumed in a pattern similar to that of afebrile periods. Possible explanations for the reduction in hot flashes during a fever include: (1) a hot flash is triggered, but the characteristic physiological changes do not occur due to competing thermoregulatory drives, (2) the febrile core temperature inhibits whatever it is that triggers a hot flash; or (3) some product of the fever process inhibits the hot flash trigger or masks the physiological changes that occur during hot flashes.