Chlorotriflouroethylene polymer oriented films

A film of semi-crystalline poly(chlorotrifluoroethylene) or a semi-crystalline copolymer of chlorotrifluoroethylene which contains up to 5% by weight of units of an ethylenically unsaturated copolymerizable organic monomer selected from the class consisting of alpha-olefins, fluorinated alpha-olefins and fluorinated ethers, which film has been oriented by stretching a substantially amorphous form of the film at least 2.5 times, at a temperature at least 40.degree. C. above the second order transition temperature at a ratio of film width to length of stretch zone of greater than 3, so that the film, after cooling under tension for two minutes at about 150.degree. C. exhibits a shrinkage of 0 to 2 percent in a first direction in the plane of the film, and a shrinkage of at least 12 percent in a second direction in the same plane as the first and which is perpendicular to the first direction.