Thiophene-S-oxides (thiophene monoxides) are relatively new compounds, less stable than the better-known thiophene-S-dioxides. They are useful as synthons for a range of applications, including in the production of pharmaceuticals. They have interesting photochemical properties, but in this presentation we contrast the electro-oxidative voltammetry of differently substituted derivatives. We also compare carbocyclic compounds such as tetracyclone, the electro-oxidation of which at relatively high potentials has never been reported in silent or insonated conditions.