Characteristic comparisons were made on various medical and dental X-ray films such as Agfa-Gevart, Dupont, Hanshin, Kodak, Konica, Nix, Sun Dental film. 1) Silver grains coated on the film base of regular and dental films showed a round (polyhedron) or potato-like shape. Grains of orthochromatic films were hexagonal or triangular in shape, although those of Konica orthochromatic films were small and round. 2) Size of silver grains ranged from 1.09 microns in the Fuji HRS film to 2.09 microns in the Konica film. 3) Thickness of the film base was the same (170 microns) in all types of film. 4) Thickness of the emulsion layer was 7 microns for non-screen type film, whereas that in the screen type was 4 microns to 8 microns. 5) Size of the silver grain of Kodak Ekta speed was large, and the thickness of the emulsion of this film was thin when compared to others. 6) In screen type films, the silver grains were only sparsely coated. In the non-screen type, however, a large number of silver grains were coated compactly on the film base. 7) Kodak TMG (T-mat) showed flattened silver grains which were piled up on the film layer.