A method of heat-treating tubing is disclosed which obtains desired performance characteristics, and more particularly to a method of heat-treating tubing which minimizes undesirable tinting and oxidation of the interior surfaces of tubing during heat-treatment by controlling the atmosphere within the tubing. This is achieved by purging the interior of the tubing with an inert gas, or a like protective atmosphere, as the tubing is advanced into an associated heat-treatment furnace. Notably, the purging is effected via the trailing ends of the tubing as it introduced into the heat-treatment furnace. Additionally, the method contemplates that a vacuum can be applied to the interior of the tubes during treatment in order to draw the protective atmosphere within the furnace into the leading ends of the tubing.