Physico-chemical experiments are reviewed and the thermodynamic properties of solid and gaseous zirconium halides of the general formula ZrXn (X = F, Cl, Br, I; n = 1-4) are evaluated and, where necessary, estimated by analogy with other metal halide systems. Thermodynamic key values at 298.15 K and heat capacity equations are tabulated up to 1500 K for the solid phase and 3000 K for the gas phase.