New data on zirconium tetraiodide (zri4) have resulted from high- temperature enthalpy and x-ray powder diffraction studies conducted by the Bureau of Mines. These studies were undertaken as part of the Bureau's efforts to provide important thermodynamic data essential to the advancement of mineral resources technologies that can be employed with minimal energy requirements and minimal environmental degradation. Enthalpies were measured with a copper- block drop calorimeter. No transitions or other anomalies were found. Tabulated values are given from 298.15 to 772 k for relative enthalpy, heat capacity, entropy, and Gibbs energy function. Enthalpies are expressed in equation form and combined with data from the literature to calculate values of the standard enthalpy of formation and the Gibbs energy of formation. X-ray powder diffraction data indicate that zri4 is primitive cubic with a lattice parameter of 11.79 A and is isostructural with stannic iodide (sni4).