Abstract: An oriented polyester film having at least one surface being roughened by containing inactive particles and three-dimensional surface roughness exponents of the said roughened surface are within ranges simultaneously satisfying the following relationships (I) to (III), while the number of coarse projections is in excess of the fourth grade:0.014.ltoreq.S.DELTA.a.ltoreq.0.025 (I)5.2.ltoreq.S.lambda.a.ltoreq.13.0 (II)0.012.ltoreq.SRa.ltoreq.0.050 (III)where S.DELTA.a represents three-dimensional average gradient, S.lambda.a represents the spatial average wavelength (.mu.m) of three-dimensional surface roughness and SRa represents three-dimensional central plane average roughness (.mu.m).

Abstract: An oriented polyester film comprising ethylene terephthalate as the major repeating unit, which comprises particles of kaolinite and calcium carbonate uniformly dispersed therein, said kaolinite and said calcium carbonate having each an average particle size of 0.05 to 0.8 micron and being contained in such amounts as satisfying the following equations:70.ltoreq.D.times.A.ltoreq.1000 (I)1000.ltoreq.A+B.ltoreq.10000 (II)0.1.ltoreq.B/A.ltoreq.25 (III)wherein D is an average particle size (micron) of calcium carbonate, A is a content (ppm) of calcium carbonate and B is a content (ppm) of kaolinite, said oriented polyester film being excellent in flatness, slipperiness, abrasion resistance, etc. with a small number of coarse particles.