A series of AM60B, die-cast magnesium alloy specimens have been examined using xray tomography at spatial resolutions from 1 – 20μm and further characterized in uniaxial tension. This paper first reports the utility of a critical strain model to link the local area fraction of porosity and the fracture strain. A discussion of the trade-off between predictive accuracy and the spatial resolution of the imaging technique is also presented in order to address the technological implications of these results. In the second half of the paper, serial tomographic imaging is used to illustrate the evolution of damage with increasing uniaxial strain. The implications are discussed with respect to numerical modeling of the performance of die-cast magnesium components.