It is reported for the first time thhat a β→ω transformation can be induced  in a β-stabilized zirconium alloy subjected to shock pressure . The ophase formed in the β matrix has been found to have a plate shape akin to martensitic plates . The lattice correspondence between the β and ω structures has been found to be the same as tha t produced by therma l treatment . The formation of the plate-shaped ω phase is explained in terms of a mechanis  involving shear on  112i planes of the bcc lattice and the mechanical instability of the β phase.