Selenium‐arsenic alloys undergo a photochemical reaction when exposed to radiation of band‐gap energy or greater. The influence of this photoinduced reaction on the electrophotographic photosensitivity of amorphous arsenic triselenide films was studied. A progressive change in the short‐wavelength photoresponse was seen in films which were exposed to intense light. The characteristics of the change depend upon the substrate temperature during the vacuum deposition of the film. Films prepared at substrate temperatures belowTginitially showed an increase in sensitivity, possibly due to structural relaxation or molecular rearrangement within the film. The initially measured spectral sensitivity of films prepared belowTgwas always lower than that for films prepared nearTg. All films eventually showed a reduction in short‐wavelength sensitivity. The rate of this change increased at elevated temperatures. The photolytic reaction itself does not affect the photosensitivity. The reduction in photosensitivity is a result of the oxidation and subsequent depletion of arsenic at the surface of the photoconductor which is enhanced by the prior photodissociation of the arsenic triselenide.