A combined process for temperature measurements in THM growth systems is described including the preparation of the source material as well as the liquid solution zone in one and the same ampoule. Using starting compositions with an excess of that component to act as the solvent the solution zone is formed during the travelling heater procedure. With thermocouples attached to the slightly modified ampoule axial temperature distributions were recorded under the usual THM growth conditions. The measurements were done in Hg0.8Cd0.2Te growing from Te-rich solution zones. The procedure described can be applied to all materials for which THM crystal growth can be achieved.