A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(P-2(J)) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of similar to 20 ms. The kinetic data at T < 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction : Delta H degrees(298) = -18.1 +/- 1.3 kcal mol(-1), Delta H degrees(0) = -17.6 +/- 1.3 kcal mol(-1), and Delta S degrees(298) = -27.7 +/- 3.0 cal mol(-1) K-1. In conjunction with the well-known heats of formation of Cl(P-2(J)) and C2C4, the above Delta H values lead to the following heats of formation for C2Cl5 at 298 and 0 K : Delta H degrees(f,298) = 8.0 +/- 1.3 kcal mol(-1) and Delta H degrees(f,0) = 8.1 +/- 1.5 kcal mol(-1). The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.