Contactant thermometry of fingers' skin in thermal functional test is a routine examination common now in vascular changes diagnosis. The sensitivity of this test is increased by the use of a linear thermograph, averaging the temperature of the skin area being examined. In order to ensure correct measurement results, conditions and principles of the test performance must be observed carefully, as indicated by the authors. Evaluation of time thermograms of fingers' skin should involve three types of thermoregulating reaction: homoiothermic, poikilothermic and amphithermic. The first type may be numbered among absolute, whereas the other two among relative physiological standards. Evaluation should include: fingers' skin temperature before cooling, the rate of temperature rise between the 1st and the 5th minute after cooling and the temperature taken at the 15th minute after cooling. Repeated measurements allow to differentiate changes in fingers' skin temperature, resulting from a damage to vessels due to vibration, as well as a relative physiological standard.