A copper constantan thin film thermocouple has been used to measure the surface temperature of a target during ion bombardment. Argon beams of 50–100 keV energy and 0–300 mwatt power have been used as heat source on a target in contact with a massive copper holder maintained at 80 or at 300K. The thermal contact has been changed from that ensured by the mechanical pressure of a metal spring to that obtained by gluing the target to the holder with a silver base paste. The surface temperature reaches a steady state value after about 150 s of bombardment and its maximum value depends on the beam power and on the quality of the thermal contact with the holder. Beam induced surface temperature increase as large as 270°C are measured in the case of a bad thermal contact and for a beam power of 300 mwatt.