A compressive split-Hopkinson pressure bar and transmission electron microscope (TEM) are used to investigate the mechanical behavior and microstructural evolution of biomedical Ti alloy deformed at strain rates ranging from 8 · 10 2 s -1 to 8 · 10 3 s -1 at temperatures between 25°C and 900°C. In general, the results indicate that the mechanical behavior and microstructural evolution of the alloy are highly sensitive to both the strain rate and the temperature conditions. The flow-stress curves are found to include both a work-hardening region and a work-softening region. The strain-rate-sensitivity parameter, b, increases with increasing strain and strain rate but decreases with increasing temperature. The activation energy varies inversely with the flow stress and has a low value at high deformation strain rates and low temperatures. Microstructural observations reveal that the strengthening effect evident in the deformed alloy is a result primarily of dislocations and the formation of a phase. The dislocation density increases with increasing strain rate but decreases with increasing temperature. Additionally, the square root of the dislocation density varies linearly with the flow stress. Correlating the mechanical properties of the biomedical Ti alloy with the TEM observations, it is inferred that the precipitation of a phase dominates the fracture strain. Transmission electron microscope observations reveal that the amount of a phase increases with increasing temperature below the b-transus temperature. The maximum amount of a phase is formed at a temperature of 700°C and results in the minimum fracture strain observed under the current loading conditions.