Hard oriented PST crystals of a Ti-48mol%Al alloy, in which lamellar boundaries are aligned parallel or perpendicular to stress axis, were creep tested over wide ranges of stress and temperature to clarify their creep characteristics. Two PST crystals of different alpha(2) spacing were used: One has the equilibrium amount of alpha(2) phase and the other contains an excess amount of alpha(2) phase. Activation energy for creep rate of the former is 350kJ/mol, being close to that for self diffusion. The other crystal having finer alpha(2) spacing provides lower creep rate due to its more significant strain hardening during the primary creep stage. This crystal shows substantially high activation energy of about 500kJ/mol. The high activation energy is discussed in conjunction with the degradation of lamellar structure that occurred during high temperature exposure.