The dissociative photoionization of 1,1-C2H2Cl2, (E)-1,2-C2H2Cl2, and (Z)-1,2-C2H2Cl2 has been investigated at high energy and mass resolution using the imaging photoelectron photoion coincidence instrument at the Swiss Light Source. The, asymmetric Cl-atom loss ion time-of-flight distributions were fitted to obtain the dissociation rates in the 10(3) s(-1) < k < 10(7) s(-1) as a function of the ion internal energy. The results, supported by ab initio calculations, show that all three ions dissociate to the same C-2v symmetry ClC=CH2+ product ion. The 0 K onset energies thus establish the relative heats of formation of the neutral isomers, that is, the isomerization energies. The experimental rate constants, k(E), as well as ab initio calculations indicate an early isomerization transition state and no overall reverse barrier to dissociation. The major high energy channels are the parallel HCl loss and the sequential ClC=CH2+ -> HCCH+ + Cl process, the latter in competition with a ClC=CH2+ -> ClCCH+ + H reaction. A parallel C2H2Cl2+ -> C2HCl2+ + H channel also weakly asserts itself. The K onset energy for the sequential Cl loss reaction suggests no barrier to the production of the most stable acetylene ion product; thus the sequential Cl-atom loss is preceded by a ClC=CH2+ -> HC(Cl)CH+ reorganization step with a barrier lower than that of the second Cl-atom loss. The breakdown diagram corresponding to this sequential dissociation reveals the internal energy distribution of the first C2H2Cl+ daughter ion, which is determined by the kinetic energy release in the first, Cl loss reaction at high excess energies. At low kinetic energy release, this distribution corresponds to the predicted two translational degrees of freedom, whereas at higher energies, the excess energy partitioning is characteristic of only one translational degree of freedom. New Delta H-f degrees(298K) of 3.7, 2.5, and 0.2 +/-1.75 kJ mol(-1) are proposed for 1,1-C2H2Cl2, (E)-1,2-C2H2Cl2, and (Z)-1,2-C2H2Cl2, respectively, and the proton affinity of ClCCH is found to be 708.6 +/- 2.5 kJ mol(-1).