The dissociation of energy-selected CH3CFCl2+ to form CH3CFCl+ was studied with a molecular-beam/threshold-photoelectron-photoion-coincidence system using synchrotron radiation for ionization. Maximal releases of kinetic energy in the channel CH3CFCl+ + Cl at five photon energies were determined from half-widths of CH3CFCl+ time-of-flight peaks in coincidence mass spectra. A thermochemical threshold for this channel was determined to be 11.10 +/- 0.09 eV after taking kinetic energy releases into account. With this threshold and heats of formation of Cl and CH3CFCl2, we derived Delta (f)H(0)degrees (CH3CFCl+) = 149.0 +/- 2.1 kcal mol(-1). Ab initio calculations were also performed to predict heats of formation of CH3CFCl2, CH3CFCl, and their corresponding cations. Our experimental results agree satisfactorily with calculations. On the basis of experimental and theoretical results, we construct an energy diagram for dissociative photoionization of CH3CFCl2 to form CH3CFCl+ + Cl.