Thermal fragmentation and rearrangement of neat phenacyl aryl sulfides I and II have been thoroughly investigated and found to involve cleavage of the C-S and C-C bonds followed by a series of H-abstraction, coupling, dimerization, rearrangement, and cyclization reactions. Also, in the presence of isoquinoline as a radical trap, I gave 1-phenyl- and 1-benzylisoquinoline in addition to the rearrangement products. Analogous results, beside SO2 arylsulfonic acid and biaryl, were also obtained on heating phenacyl aryl sulfones III and IV in tetraline. A suitable mechanism has been suggested to account for the isolated products.