The dissociative ionization of 13 nitro derivatives of 2(4)-azafluorenes and 2(4)-azafluorenones was investigated. The introduction of an electron-acceptor nitro group into the molecule markedly reduces the stability of the molecular ions and suppresses the fragmentation pathways that are characteristic for azafluorenes. Nitro-nitrite rearrangement proceeds more readily in nitro-substituted 4-azafluorenes than in nitro-substituted 2-azafluorenes. A characteristic feature of the fragmentation of azafluorenes that do not contain nitro and methyl groups in a vicinal orientation is elimination of a OH particle by the molecular ions. It was established by deuterium labeling that in this case the formation of an [M - OH]+ ion is due to the presence of a methylene group attached to the C9 atom in the molecule. © 1982 Plenum Publishing Corporation.