Magnesium alloys always exhibit a high directional anisotropy owing to their hexagonal crystal structure, which limits the modes available for plastic deformation and give rise to significant intergranular stresses. Particularly wrought magnesium alloys tend to display a strong in-plane tension-compression asymmetry. This phenomenon has been attributed to mechanical twinning during compression along the prior working direction but not during tension along the same direction. The twins formed by plastic straining can be destroyed again when the sense of loading is reversed. The main objective of this proposed study is to addresses an important, but yet unresolved, question in the field: how does the twin reversal mechanism affect fatigue life of magnesium alloys? We propose to investigate the twinning/slip balance during low cycle fatigue at various temperatures.