The mass spectra of a series of arenesulphonamides and some representative sulphonyl chlorides are reported and discussed. The sulphonyl chlorides and the primary arenesulphonamides have prominent rearrangement ions in their spectra owing to loss of the elements of SO₂ from the molecular ions, whereas the sulphonamido-groups of N-alkyl and dihydrophenanthrenesulphonamides are not involved in skeletal-rearrangement processes. Fragmentation modes have been established by high resolution measurements and metastable ions.