Fatigue failure occurs under prolonged load at lower stress levels than the static strength, which can lead to unexpected, catastrophic failure. Especially for materials used in medical engineering and as implant material this risk must be minimised. Molybdenum rhenium alloys exhibit a high ductility and strength, consequently a good fatigue behaviour, as well as good biocompatibility, thus they will be a promising candidate to replace conventional Ti-based implants in future. Their application is limited by the costs and scarcity of rhenium. This thesis investigates the high cycle fatigue behaviour of two different molybdenum rhenium alloys, with a rhenium content of 47.5 wt% and 41 wt%, respectively. Therefore, rotary bending tests were performed on the molybdenum rhenium alloys, as well as a detailed microstructure analysis was conducted. Additionally, the fatigue fractures of the tested specimens were analysed. Both alloys show similar endurance limits and fatigue strength. An influence of the rhenium content on the S-N curves is not observable. The fracture surfaces show typical characteristics for fatigue failure and show distinguishable features for each alloy.