The electronic structures and the gas-phase thermolyses of the 2-tetrazenes have been studied by He(I) photoelectron spectroscopy. The compds. are characterized by at least three ionization potentials with energies less than 10 eV which are assigned to the MOs p3 (HOMO), n+, p2, and n-. In the thermolyses either the formal disproportionation products (amine and imine) of the resp. aminyl radical are found, or the latter is stabilized by loss of alkyl radical affording also an imine. Further products which can be explained by radical reactions are detected in flash vacuum pyrolyzes. The tricyclic cis-2-tetrazene I is cleaved by [2 + 2 + 2] cycloreversion. The methoxymethyl-substituted compd. II exhibits a more complex cleavage pattern.