The martensitic transformation behaviour, after thermomechanical treatment of the TiNi-alloy with two-way shape memory, have been studied by differential scanning calorimetry. The results are correlated with electrical resistivity and electron microscopical observations. One heating and cooling cycle in the martensitic temperature range (−60/+70 °C) is recorded in order to separate the respective transformation processes involved. DSC curves of a series of sequential cycles illustrate the reversibility of the pre-martensitic structural change. Additionally, evidence is sought for the tetragonal lattice distortion which can occur in the austenitic lattice after heating up to 200 °C. All the observations showed that DSC is an important tool in the investigation of complex phase transitions.