Other than triarylamines, which are protonated by strong acids both at their N-atom and aromatic rings, pyrrole and its N-substituted derivatives were exclusively protonated at the carbon atoms of their heteroaromatic rings. Whereas with the strong trifluoromethane sulfonic acid (TFS) stable pyrrolium salts were obtained, with the weaker trifluoroacetic acid (TFA) oligomers are formed. E.g., from the N-(tert-butyl)pyrrole a dimeric compound could be unambiguously identified and structural characterised by means of ¹H NMR measurements. Treatment of N-aryl substituted pyrroles with deuterated TFS revealed an H/D exchange not only at the pyrrole rings but also at their aryl moieties even.