This paper presents the results of a study on the influence of microstructure on the corrosion behavior of a alpha-beta Ti-5%Ta-1.8%Nb alloy-a candidate material for use in high concentrations of boiling nitric acid. The "as cast" alloy had a lamellar structure and showed a corrosion rate of about 1.5 mpy. Thermo-mechanical processing of the cast alloy resulted in a structure of predominantly of equiaxed alpha with random distribution of fine beta particles. This "reference" structure was further modified employing different heat treatments similar to that for commercial titanium alloys such as mill annealing, solution treatment and aging or over aging treatments. Corrosion rates evaluated in boiling nitric acid in the liquid, vapor and condensate phases, showed low values similar to 1 mpy. Of these, the lowest corrosion rate (similar to 0.03 mpy) was exhibited by the structure with minimum amount of beta phase, distributed in an equiaxed alpha matrix. This structure was obtained by aging of the solution treated "reference" alloy. Hence, solution treatment high in the alpha + beta phase field followed by aging at a temperature low in the alpha + beta phase field has been identified as the optimum treatment to obtain a microstructure with superior corrosion resistance.