1. Tests on thermistors have shown that the prolonged effect of negative and room temperature does not disturb stability by more than 0.5°C over a prolonged period, in any case not less than three to four years. 2. The prolonged effect of high temperature (50–80°C) results in aging of the thermistors, disregard of which can result in errors up to 3–5°C for individual thermistors, but for the majority of tested thermistors the errors did not exceed 0.5–1°C. 3. When a greater measurement accuracy than ±0.5°C is required the thermistors must be aged at a temperature around 100°C for several weeks [3]. 4. A check on the accuracy of the thermistor resistance-temperature relationships usually adopted indicated that within the calibration range 40–50°C this is valid with an accuracy to 0.5°C. At a removal from the calibration range of 30–40°C, deviations of the actual relationship from the assumed can amount ot 1–2°C. In order to eliminate these errors, particularly at negative temperatures, the calibration data must be extrapolated in accordance with more accurate R=f(T) relationships, or the calibration must embrace the whole range of possible temperatures, including intermediate points. 5. The tests, in addition to many years experience with semiconductor resistance thermometer in full-scale and laboratory investigations, have fully confirmed their high quality and have indicated possibilities of using this type of telethermometer for investigations on hydraulic engineering structures.