Telomerization of allyl ethene sulfonate (AES) in the presence of butyl mercaptan yielded a mixture of two products: the first was a five-membered ring sultone containing a sulfide group and the second a five-membered ring sulfonium salt formed by reactionofthe sultone of theJustproduct with its own sulfide function. If cyclotelomerizations and cyclopolymerizations give the same ring structures, these results indicate that the cyclic units in poly-AES are five-membered rings. Telomerization of allyl allyl sulfonate (AAS) in the presence of butyl mercaptan yielded a mixture of two products formed by addition of butyl mercaptan to one of the two allyl functions. Telomerization of AAS in bromotrichloromethane yielded a small amount of 1,5-hexachIoro-3-bromopentane formed via fission of an oxygen-carbon bond, and a rearranged adduct. The rearrangement of the allyl group to a propenyl group in the case of AAS was not observed when allyl ethane sulfonate or propyl allyl sulfonate were telomerized under the same conditions. Therefore a mechanism is proposed in which the rearrangement of the allyl double bond in AAS is due to the presence of a second double bond in the same molecule. This observation also indicates that poly-AAS might have a more complicated structure than expected from a simple cyclopolymerization mechanism.