Abstract: A method is provided for the production of ultrathin films having a thickness of 2.5 microns or less, including film having a thickness as low as about 0.2 microns. Film of thermoplastic polymer, preferably polyester film, less than 25 microns in thickness and in thermal equilibrium with the surrounding air is simultaneously stretched at least twice and up to about five times its original dimensions in the machine and cross-machine directions under conditions such that thicker regions are maintained at an elevated temperature by radiant heating and at least a 0.1.degree. C. temperature differential is established between the thicker (hotter) regions and the thinner (cooler) regions of the film prior to stretching the film beyond its elastic limit.