A fretting fatigue test method in a simulated body fluid is shown to evaluate fatigue properties of metallic materials which are used in the orthopaedics field. Next, fatigue/fretting fatigue behavior in a simulated body fluid is given for 316L stainless steel, Ti-6% Al-4% V alloy, pure Ti for industrial use and Co-Cr-Mo alloy. Finally, we discuss the relationship between the tensile strength and the fatigue strength/fretting fatigue strength of metallic biomaterials at 107 cycles in air and in a simulated body fluid. For all of the biomaterials tested, the fatigue strength at 107 cycles is similar in air and in a simulated body fluid. The fatigue strength is closely correlated to the tensile strength: The fatigue strength increases with increasing tensile strength. However, a correlation is not observed between the fretting fatigue strength at 107 cycles and the fatigue strength or the tensile strength.