Measurements were made of the extremes in temperature which occur at different sites in the oral cavity during fluid intake. The results indicate that temperatures noted at the tooth surface, within the mouth, during fluid intake were less than the temperatures of the fluid imbibed. Variations in temperature were noted in different areas of the mouth. This may be associated with the position of the tongue during swallowing and the effect of the tissues of the oral cavity as heat absorbers. The range of temperatures noted at the tooth surface and the duration of the temperature changes were at variance with those utilized in many thermocycling studies. It is suggested that closer alignment with the clinical situation is desirable.