Laser desorption ionization (LDI) time-of-flight (TOF) mass spectroscopy of solid p-dimethylaminophenylpentazole (1) gives strong peaks of m/z -42 and -70. The -70 peak was identified by 1 5 N labeling of 1 to be the pentazolate anion (cyclo-N 5 - ). The pentazolate anion is formed by an electron attachment to 1 forming the corresponding radical anion followed by a decomposition into 4-N(CH 3 ) 2 -C 6 H 4 and (cyclo-N 5 - ). The LDI TOF experimental study also revealed that the (cyclo-N 5 - ) is very stable. These conclusions are supported by QM calculations at the B3LYP/6-311+G(2df,p) level.