Abstract: A radiation endoscope is described wherein a laser or other radiation source is employed for therapeutic purposes. Radiation energy may be accurately directed at a target in a body cavity with the use of a marking spot whose light energy is passed along an optical path in the sheath of the radiation endoscope to the cavity area on which the radiation beam is incident. Eye protection for an operator of the radiation endoscope is obtained with the use of a variable filter interposed in an image path and coupled to correspondingly reduce the beam radiation effective in the body cavity as the image path transmissivity is enhanced. In one embodiment, attenuation of beam radiation is obtained by using a variable density optical filter coupled to the filter operative in the image path. In another embodiment, radiation beam attenuation is achieved by deriving a radiation beam control signal from the filter operative in the image path.