Unimolecular fragmentations for the fluoranthene radical cation were studied by time-resolved photoionization in the vacuum UV, RRKM/QET calculations, and MS/MS with electron ionization. The major reactions observed are parallel H-. and H-2 losses, as well as consecutive H-. losses. These take place without prior isomerization to the more stable pyrene radical cation structure. Activation parameters were deduced for the reactions. Appearance energies were determined for the microsecond and millisecond time ranges. The H-. loss reactions are characterized by loose transition states and have no reverse activation energies. This has enabled the determination of new thermochemical data. The heat of formation of the product cation of the H-. loss reaction is Delta H(fo)degrees(C16H9+) = 307.6 kcal/mol. The C-H bond energy in the fluoranthene radical cation is 4.38 eV.