Systematic studies on the photo-Fries rearrangement of different 9H-carbazol-2-yl sulfonates 2 have shown that this type of conversion can be readily used for the preparative-scale introduction of alkyl-or arylsulfonyl groups into polycyclic aromatic compounds under very mild conditions. A series of new 1-sulfonyl-(3) or 3-sulfonyl-9H-carbazoles (4) were prepared in medium-to-good yields, and characterized by UV/VIS, 1 H-NMR, and 13 C-NMR spectroscopy, as well as by elemental analysis. Effects of irradiation wavelength, solvent polarity, presence or absence of O 2 , and photosensitizers were studied in detail.