Elimination of a substituent from the 9-position appears to be the main pathway for decomposition of 9-amino-4-azafluorenes. An amine type fragmentation pattern has been observed as well. Decomposition of 9-spiro-4-azafluorenes occurs via cleavage of the radical bound to the three-membered ring. 9-Alkyl-(dialkyl)-1- and 4-azafluorenes also readily lose a substituent in position 9. The observed pathways and principles allow one to determine the nature of the substituent in the 9-position and also to differentiate 1-azafluorenes from 4-azafluorenes. © 1988 Plenum Publishing Corporation.