Many anomalous phenomena have been observed in NiTi alloys above martensite start temperature, such as softening of the shear constants, increase of internal friction and diffuse scattering of TEM. However, little information has been obtained about the change in the electron system of the parent phase prior to the martensitic transformation, which should be the origin of all pre-martensitic phenomena. In this work, the temperature change of positron annihilation lifetime, which is quite sensitive to electronic-structural changes of matter, were carried out for NiTiCu alloys. The alloys show martensitic transformation from a B2 (cubic) phase to a B19 0 (monoclinic) phase via a B19 (orthorhombic) phase as the temperature is lowered. We have found anomalous positron lifetime changes in Ni 10 Ti 50 Cu 40 and Ni 15 Ti 50 Cu 35 alloys which show a B2-B19-B19 0 phase transformation. Positron lifetime increases anomalously with decreasing temperature at temperatures higher than the transformation temperature into a B19 0 phase. On the other hand, positron lifetime does not show any anomaly in the B2 phase of Ni 30 Ti 50 Cu 20 alloy which shows B2-B19 phase transformation. The positron lifetime of the parent B2 phase shows good agreement with the theoretically-calculated value. Those of the martensite phases of B19 and B19 0 , although, are about 30 ps longer than calculated ones. This big difference between experimental and calculated positron lifetimes cannot be explained by any existing theory.