Phenylnitrene radical cations m/z 91, C6H5N, 8a(center dot+) are observed in the mass spectra of 1-, 2-, and 5-phenyltetrazoles, even though no C-N bond is present in 5-phenyltetrazole. Calculations at the B3LYP/6-311G(d,p) level of theory indicate that initial formation of the C-phenylimidoylnitrene 13(center dot+) and/or benzonitrile imine radical cation 19(center dot+) from 1H- and 2H-5-phenyltetrazoles 11 and 12 is followed by isomerizations of 13(center dot+) to the phenylcyanamide ion 15(center dot+) over a low barrier. A cyclization of imidoylnitrene ion 13(center dot+) onto the benzene ring offers alternate, very facile routes to the phenylnitrene ion 8a(center dot+) and the phenylcarbodiimide ion 14(center dot+) via the azabicyclooctadienimine 16(center dot+). Eliminations of HNC or HCN from 14(center dot+) and 15(center dot+) again yield the phenylnitrene radical cation 8a(center dot+). A direct 1,3-H shift isomerizing phenylcarbodiimide ion 14(center dot+) to the phenylcyanamide ion 15(center dot+) requires a very high activation energy of 114 kcal/mol, and this reaction needs not be involved. The benzonitrile imine-3-phenyl-1H-diazirine-phenylimidoylnitrene-phenylcarbodiimide/phenylcyanamide rearrangement has parallels in thermal and photochemical processes, but the facile cyclization of imidoylnitrene 13(center dot+) to azabicyclooctadienimine 16(center dot+) is facilitated by the positive charge making the nitrene more electrophilic. Furthermore, the benzonitrile imine radical cation 19(center dot+) can cyclize to indazole 24(center dot+), and a series of intramolecular rearrangements via hydrogen shifts, ring-openings and ring closures allow the interconversion of numerous ions of composition C7H6N2 center dot+, including 19(center dot+), 24(center dot+), the benzimidazole ion 38(center dot+) and o-aminobenzonitrile ion 40(center dot+), all of which can eliminate either HCN or HNC to yield the C6H5N center dot+ ions of phenylnitrene, 8a(center dot+), and/or iminocyclohexadienylidene, 34(center dot+). Moreover, benzonitrile imine 19(center dot+) can behave like a benzylic carbenium ion, undergoing a novel ring expansion to cycloheptatetraenyldiazene 45(center dot+). The N-phenylnitrile imine ion 2d(center dot+) derived from 2-phenyltetrazole Id cleaves efficiently to the phenylnitrene ion 8a(center dot+) but may also cyclize to the indazole ion 24(center dot+). The N-phenylimidoylnitrene 59(center dot+) derived from 1-phenyltetrazole 5d undergoes facile isomerization to the phenylcyanamide ion 15(center dot+) and hence phenylnitrene radical cation 8a(center dot+).