Abstract: The invention relates to a single-layer biaxially oriented polyester film which, together with good processing performance, after it has been metalized or has been coated with oxidic materials, has very good gas or oxygen barrier properties, and which has been built up from one base layer, where the film has a planar orientation &Dgr;p of greater than 0.166. For at least one surface of the film, the number N of elevations per mm2, the height n in &mgr;m, and the diameter d in &mgr;m of the elevations are linked by the following equations: - 1 - 3.7 * log ⁢   ⁢ h / μm < log · N / mm 2 < 2.48 - 2.