Trimethyl- or dimethylphenylsilylepoxides react with lithium phenylsulfide to give regio- and stereodefined vinyl sulfides resulting from alpha-ring opening and Peterson elimination. When the epoxide bears the bulky tertbutyldiphenylsilyl group the reaction is more puzzling. Depending on the beta-substitution and the presence of aluminium chloride, we obtained silyl enol ethers, alpha-silylaldehydes or alpha-hydroxy-beta-phenylthiosilanes, all resulting from beta-opening. (C) 2000 Elsevier Science Ltd. All rights reserved.