The variations in thermal transformation properties due to annealing within the temperature range from 400°C to 600°C were studied for the near equiatomic Ni-Ti shape memory alloy by the Differential Scanning Calorimetry (DSC) measurements. There was a critical temperature (about 600ºC), where the specimens demonstrated remarkably different transformation courses. There were also noticeable changes in transformation temperatures and heats depending on the annealing temperature. It is thought that the alterations of the microstructure in the Ni-Ti alloy during annealing are responsible for such behavior.