The dissociation of the naphthalene radical cation has been reinvestigated here by a combination of tandem mass spectrometry and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). Six reactions were explored: (R1) C10H8 center dot+ -> C10H7+ + H (m/z = 127); (R2) C(10)H8(center dot+) -> C8H6 center dot+ +C2H2 (m/z = 102); (R3) C10H8 center dot+ -> C6H6 center dot+ + C4H2 (m/z = 78); (R4) C10H8 center dot+ -> C10H6 center dot+ + H-2 (m/z = 126); (R5) C10H7+ C6H5+ + C4H2 (m/z = 77); (R6) C10H7+ -> C10H6 center dot+ + H (m/z = 126). The E-0 activation energies for the reactions deduced from the present measurements are (in eV) 4.20 +/- 0.04 (R1), 4.12 +/- 0.05 (R2), 4.27 +/- 0.07 (R3), 4.72 +/- 0.06 (R4), 3.69 +/- 0.26 (R5), and 3.20 +/- 0.13 (R6). The corresponding entropies of activation, Delta S-1000K double dagger, derived in the present study are (in J K-1 mol(-1)) 2 +/- 2 (R1), 0 +/- 2 (R2), 4 +/- 4 (R3), 11 +/- 4 (R4), 5 +/- 15 (R5), and -19 +/- 11 (R6). The derived E-0 value, combined with the previously reported IE of naphthalene (8.1442 eV) results in an enthalpy of formation for the naphthylcation, Delta H-f degrees(0K) = 1148 +/- 14 kJ mol(-1)/Delta H-f degrees(298K) = 1123 +/- 14 kJ mol(-1) (site of dehydrogenation unspecified), slightly lower than the previous estimate by GotIcis and co-workers. The derived E-0 for the second H-loss leads Delta H-f(o) for ion 7, the cycloprop[a]indene radical cation, of Delta H-f degrees(0K) = 1457 +/- 27 kJ mol(-1)/Delta H-f degrees(298K)(C10H6+) = 1432 +/- 27 kJ mol(-1). Detailed comparisons are provided with values (experimental and theoretical) available in the literature.