Photolysis of benzyl β-naphthyl sulfoxide results mainly in α-cleavage. The isomeric sulfenic ester is the major product. Because the triplet energies of both the sulfoxide and sulfenic ester are below that of acetone, in contrast to the previously studied phenyl and total cases, interpretation of sensitization experiments is straightforward. The sulfinyl radical is characterized by transient absorption and a model is proposed to account for its reactivity with nitroxide radicals.