Method making it possible to control the temperature prevailing inside a high-temperature oven employed for the treatment of a synthetic yarn, especially during an operation of texturing by false twisting, said method consisting, in the case of a given substance (count and chemical composition), in modifying the temperature inside the oven as a function not only of the speed of travel of said yarn, but also of its count.It is characterized in that said temperature .THETA. in .degree.C. is determined from the general formula:.THETA.=aV+bin which:- V is the speed of travel of the yarn inside the oven in meters per minute (m/min);- a denotes a linear variation coefficient (or slope), itself a function of the count expressed in decitex (dtex);- b denotes a correction factor which is a constant whose value is also determined as a function of the count of the yarn in decitex (dtex).