Two types, A and B, of Zr-2.5Nb samples were subjected to compression tests. Both samples consisted of similar microstructure - hexagonal closed packed (hep) a phase (the primary phase) and grain boundary bcc (body centered cubic) β phase. However, the hardness of the b phase differed between the samples respectively being hard (sample A) and soft (sample B) relative to the primary phase. This difference was caused by the presence of fine w precipitates. The relative hardness of b phase determined almost all aspects of deformed microstructure developments. In sample A, the primary phase had higher lattice strain and in-grain misorientation developments. In sample B, on the other hand, the softer b phase was clearly linked to more deformation twinning and associated grain size refinement and 'texturing' of the hep a phase.