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This paper examines fatigue crack paths in coarse-grained magnesium alloys.Visualization of the microstructure by etching and continuous crack monitoring with amicroscope provides evidence of the crack-grain interaction at different fatigue crack growthregimes. Near-threshold fatigue crack growth promotes the development of rough surfaces byactivation of single slip mechanisms and crack deflection. The R-ratio effect on near-threshold results is discussed in the light of the partial crack closure model. The role of grainboundaries and grain-to-grain crack deflections on fatigue crack growth rates is determined.