A marking tape for transferring information written thereon to a film when the film is exposed to x-rays. The tape is a laminate of an upper film, a radiopaque emulsion, and a lower film. The top surface of the upper film is partially coated with a writable ink, and the ink coating positioned directly over the radiopaque emulsion. Pressure exerted by the user while writing on the ink surface causes the underlying emulsion to part. When the marking tape is affixed to a film cassette, x-rays penetrate the marking tape in those areas where the emulsion has been parted, the underlying film is exposed, and the information entered on the marking tape is thereby transferred to the film. The marking tape can be made in different sizes and radiopacities that can be distinguished by color-coding the writable surface.