The metallurgy and superconductivity of the Nb-Ti-Ta ternary alloy system were studied. The Nb-Ti, and Ta-Ti binary samples, and Nb-Ti-Ta ternary samples were precipitation heat treated under different schedules. After the precipitating heat treatment, the samples were characterized by X-Ray Diffraction (XRD) techniques. Equilibrium binary and ternary phase diagrams based on the different alloy compositions and heat treatment temperatures were developed. The Ta-Ti binary phase diagram is very close to the ASM standard phase diagram. The ��-phase boundary of Nb-Ti binary phase diagram developed here is at a higher temperature relative to the ASM standard one. A working ternary equilibrium phase diagram for the Nb-Ti-Ta system has been developed that is based on the experimental measurements and quantitative thermodynamic calculations. Measurements of superconducting critical temperature, Tc, show a good agreement with previous measurements of Tc in the ternary alloys. / Graduation date: 2002