[en] Information on the physical, chemical, and mechanical properties of thoria and thoria-urania is reviewed and assessed. The properties discussed are those judged to be important for an understanding of the behavior of these oxides as nuclear fuel materials. Evaluation was made, where possible, of the effects of composition, material variables, temperature, and irradiation exposure. Data were taken from a review of the literature and from both published and unpublished data derived from the Light Water Breeder Reactor (LWBR) Program at the Bettis Atomic Power Laboratory. 30 figs., 23 tables, 163 refs