Structural-phase states and properties of weakly stable Ti-Ni-based alloys during thermal cycling are analyzed. A review based on representative interesting database on multicomponent Ti(Ni, Co, Mo) alloys with shape memory effect is presented. It is demonstrated that the nonlinear character of the change in the temperature dependences of the electric resistance in Ti(Ni, Co, Mo) alloys during thermal cycling and thermal treatment in the region preceding the martensitic transformation reflects the presence of the region of weakly stable pre-transitive states near the stability loss boundary. Extraordinary influence of thermal cycling through the region of martensitic transformations on the temperature dependences of curves of the electric resistance in a microalloyed multicomponent titanium-nick-elide-based alloy is established. It is important that thermal cycling in the examined alloys finishes its essential influence on the MT by the 10th cycle. Results obtained allow us to state that the influence of thermal cycling through the MT region in alloys with well expressed weakly stable pre-martensitic state leads to the development of phase work-hardening with a wide spectrum of defects. These defects also influence the mobility of interphase boundaries and can contribute considerably to an increase in the centers of electron scattering. Experimental data demonstrate the weak stability of structural phase states of the system near the stability loss boundary for structural phase interconversions. In the approximation of the thermodynamic probability of realization of these states in the case of finite temperatures it is possible to expect their coexistence in one system or interconversions under the minimal action of the thermal force.