A compressive split-Hopkinson pressure bar apparatus and transmission electron microscopy (TEM) are used to investigate the deformation behaviour and microstructural evolution of Ti-15Mo-5Zr-3Al alloy deformed at strain rates ranging from 8 x 10(2) s(-1) to 8 x 10(3) s(-1) and temperatures between 25 degrees C and 900 degrees C. In general, it is observed that the flow stress increases with increasing strain rate, but decreases with increasing temperature. The microstructural observations reveal that the strengthening effect evident in the deformed alloy is a result, primarily, of dislocations and the formation of alpha 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. The amount of alpha phase increases with increasing temperature below the beta transus temperature. The maximum amount of alpha phase is formed at a temperature of 700 degrees C and results in the minimum fracture strain under the current loading conditions.