Sunlight photolysis of 4,5-diphenylisoxazole (1) in methanol sensitized by benzophenone gives 4,4',5,5'-tetraphenyl-2,2'-bioxazole, (4). On irradiation at 350 nm in acetone or at 253-7 nm in absolute alcohol, isoxazole (1) yields ct-benzoylphenylacetonitdle (_6) besides the expected phenanthro [9,10-d]-oxazole (~). The bioxazole and the ketonitrile have been identified by single crystal X-ray studies.