Thorium-zirconium-uranium and thorium-zirconium alloys were prepared by direct melting of the metals, of 99.6-99.9per thousand purity, in an arc furnace in an atmosphere of chemically pure argon. The alloys were then heated in evacuated quartz tubes at 1000° for 24 hrs., and quenched in ice water. Determinations of the mechanical strength were made after quenching, and also after tempering of the quenched alloys by heating at 500° for 1000 hrs. and cooling in air. In the last case, determinations of elongation were made at 500°. The experimental results are presented in the form of curves expressing the tensile strength, elongation, cross-sectional contraction, and hardness as functions of the composition of the alloys. The observed variations in mechanical strength of the alloys were apparently related to changes in the phase composition at different temperatures, to decomposition processes in the solid solution, to martensite transformation, and to coagulation of finely dispersed particles. All alloys were tested for their corrosion resistance in water at 350° and their resistance to oxidation by air at 400 and 500°. As determined by these tests, the corrosion resistance was low: most alloys showed extensive corrosion after 100 hrs. in hot water. Similarly, the alloys showed a low resistance to air oxidation. Depending on their composition, the alloys were completely oxidized at 400° within 100-700 hrs.