Thin Films of thicknesses less than 1000 Å have been deposited in a vacuum of 5 × 10-5 Torr by the very fast evaporation (∼50 Å/s) of the ternary Se10Sb10Te80 bulk alloy pieces onto cleaned glass plates which were held at room temperature vertically above the evaporation source (at a distance of 25 cm). From the energy dispersive X-ray analysis (EDAX) patterns of the films, the presence of Te, Sb and Se has been confirmed and the semi-quantitative content of the constituent elements in the alloy films has been determined. Film specimens for transmission electron microscopy have been detached from these glass substrates by dippping the latter in very dilute HF solution. These film specimens have been examined in an electron microscope. Electron diffraction patterns reveal that the films are not amorphous but are polycrystalline in most of the regions, but also single crystalline in some regions which have a darker contrast in bright field transmission electron micrographs. Analysis of the single crystalline (spot) patterns obtained reveals that the single crystalline microcrystallites in different regions are oriented differently. The orientations of these microcrystallites have been determined.