The gamma <----> alpha(2) phase transformation in fractured high temperature stress rupture Ti-48Al-2Nb(at.%) alloy has been studied by analytical electron microscopy. alpha(2) and gamma phases were found at grain boundaries. alpha(2) layers that suspended in gamma layers and interfacial ledge higher than 2d((111)gamma) at gamma/alpha(2) interfaces were observed in the lamellar grains. These facts indicated that gamma <----> alpha(2) phase transformation and dynamic recrystallization have occurred during high temperature stress rupture deformation. It can be concluded that deformation induced gamma <----> alpha(2) phase transformation and dynamic recrystallization resulted in the presence of gamma particles at grain boundaries. A structural and compositional transition area between deformation-induced alpha(2)(or gamma) and its adjacently original gamma(or alpha(2)) phases was found by HREM and EDS and is suggested as a way to transform between gamma and alpha(2) phase during high temperature stress rupture deformation. The transition area was formed by slide of partial dislocations on close-packed planes and diffusion of atoms.