Biaxially oriented poly(ethylene terephthalate) films have been characterized using scanning force microscopy (SFM). Comparison of SFM topographical and SEM data revealed that the SFM provides superior lateral resolution and direct access to height data. Structural details absent from the SEM images were revealed by SFM, including radiating features observed around the silicate inclusions, tentatively attributed to local strain-induced crystallization. Lateral force microscopy (LFM) revealed high contrast on the surfaces of the silicate additives in the forwards scan direction, and inverted contrast in the reverse direction, indicating a substantial and unexpected friction interaction between the SFM tip and the silicate particles. Force modulation microscopy (FMM) images exhibited unexpectedly low contrast for the silicates, while the perimeters of silicate particles were found to be delineated with striking clarity. FMM contrast was sharply dependent on imaging parameters, including, in particular, the amplitude of oscillation and the scan speed.