Catalytic amounts of aminium salts A-U induct the conversion of methylene chloride in solutions of several ally1 and diallyl episulphidcs 1-6 into the corresponding unsaturated derivatives 7- 12. The desulphuriwtion process, which occurs through a plausible chain electron-transfer mechanism, rapid and may proceed in a fashiont hat preservest he stereochemistryo f the starting episulphide.