3-R-5-Nitro-1, 2-benzisothiazole derivatives (1, R= substituents) in solution, undergo photochemical isomerization to produce 2-R-5-nitro-1, 2-benzothiazole derivatives. Here, generalizations and limitations by the substituent, solvent, and excitation wavelength for the photoisomerization reaction of 5-nitro-1, 2-benzisothiazoles are reported.