N-Alkylation of 6(7)-R-1,5-dinitro-3-methyl-3-azabicyclo[3.3. I]non-6-enes with methyl iodide afforded a series of quaternary ammonium salts whose yield depended on the solvent polarity and character of substituents located in positions 6 or 7 of substrate. The presence of electron-withdrawing groups reduced the yield of the target products compared to unsubstituted compound, whereas the electron-donor substituents increased the yield. As shown by the X-ray diffraction study the congormation of the substances was not changed in the course of quaternization. The DTA-TG analysis revealed that in the first stage of thermolysis the 6(7)-R-3,3-dimethyl-1,5-dinitro-3-azoniabicyclo[3.3. I]non-6-ene iodides suffer dealkylation. Two fragmentation paths of compounds synthesized under electron impact were observed: elimination either of methyl iodide or aziridinium cation.