This paper deals with heat flow in the spindle head of machine tools and with the methods which decrease thermal displacements of the spindle, especially in Z axis direction. Simple analytical method of heat.flow and temperature rise has been developed for the estimation of the heat load on the spindle. This method was applied to the spindle heads of the model and the actual machining center. The results show that the calculated temperature rises fairly agreed with those measured, and the adaptations of ceramic ball bearings and fins at spindle noze decreased thermal displacements of the spindle.