Newly developed low-modulus β-type titanium alloys such as Ti-29Nb-13Ta-4.6Zr (TNTZ) and Ti-Cr alloys are expected to be used for rods in spinal fixation devices. As the endurance, i.e., fatigue strength, is one of the most important factors for this application. Various types of fatigue strengths of TNTZ and Ti-Cr alloys as well as their developments were investigated. Compared to conventional Ti-6A1-4V extra low interstitials (ELI) for biomedical applications the uni-axial fatigue strength of TNTZ is increased significantly by thermomechanical processing, which includes solution treatment, severe cold swaging or rolling, and followed by aging treatment. The uni-axial fatigue strength of Ti-12Cr is significantly higher compared to that of Ti-6A1-4V ELI. The four point bending fatigue strengths of the alloys exhibit opposite trends.