Öz The martensites produced by plastic deformation in the austenite strueture of Ti-62 % Ta alloys are needle-like martensites and are called as strain-induced martensites. These deforma­ tion Products are formed in the configuration of parallel lines in austenite matrix and contain cıy^stallographic properties similar to those of other Ti-Ta alloys. These martensites have been to a certain crystallographic direetion in the parent phase which is [101 of the austenite crystal strueture. The crystallographic direetion of twinnings, which produced in austenitic region and advanced in martensite by the effecc of plastic deformation, was found as [ÖIO]^ and [1120 ]•jm relatively in the parent and pröduct phases. The crystal structnres of the phases were determi- ned as body-centered cubic (bcc) and hexagonal close-packed (hep). In addition to the defor­ mation thvinnings mentioned above, the twinnings which created in two other direetions have also beeıı observed and their crystallographic direetions were found as [1011 ]j^ and [1101], in the produet, and [110]^ and [112 in the parent phases.