Recently concerns about the Ni-hypersensitivity and toxicity of Ni have stimulated the development of Ni-free biomedical shape memory alloys. The b-Ti alloys are promising candidates for biomedical shape memory alloys. In this study, the shape memory effect and superelasticity of Ti-Nb based alloys were investigated. Effects of alloying element and heat treatment condition on microstructure, martensitic transformation and deformation behavior was investigated by tensile tests at various temperatures, thermal cycling tests at various stresses, X-ray diffractometry and transmission electron microscopy. The shape memory effect and superelasticity were observed in Ti-Nb binary alloys. However, the low critical stress for permanent deformation caused the superelasticity not to reveal a large recovery strain and recovery stress at room temperature for the Ti-Nb binary alloys. Addition of alloying elements such as Zr, Ta, Pt, Au and O was effective in stabilizing the shape memory and superelastic properties. Aging treatment and low temperature annealing were also effective in increasing the critical stress for permanent deformation, resulting in excellent superelasticity in Ti-Nb based alloys.