[en] Geochemical reactions are typically defined in terms of a mass-action law that contains a thermochemical constant, such as an equilibrium constant or the related free energy of reaction at standard conditions. A well-defined set of thermochemical data is thus necessary for accurate prediction of the geochemical behavior of the radionuclides in the repository environment. Therefore, the available thermochemical data for the radionuclides thorium, plutonium, americium, and curium were compiled and reviewed. The scheme used in the review of the available literature is illustrated. The principal components of the review are selecting relevent oxidation states for the radionuclides; preparing a comprehensive tabulation of the data; selecting the solids and aqueous species likely to be important in the repository environment, based on solubility and speciation diagrams for each oxidation state under the expected repository conditions; evaluating the sources of the tabulated data, and generating recommendations for future research priorities for the Salt Repository Project. 263 refs., 15 figs., 72 tabs