Introduction A rise in body temperature (Tb) is known to cause minute ventilation (VE) to increase. However, the mechanism of the ventilatory response to rising Tb is still unclear. In the context of the relationship between VE and Tb, it is known that respiratory chemosensitivity is influenced by Tb, and that a rise in Tb of more than 0.7 °C enhances respiratory chemosensitivity . It is not known, however, whether increases in Tb less than 0.7 °C also influence respiratory chemosensitivity. The aim of this study was to clarify the effect of mild hyperthermia (0.3 °C and 0.7 °C) on respiratory chemosensitivity.