Grain refinement of a cast Mg-9% Al alloy was attempted using equal-channel angular pressing (ECAP). It is shown that the introduction of extrusion before ECAP is important in order to refine the grain size successfully through ECAP without breaking the sample: this combined process is designated EX-ECAP. Static annealing experiments were conducted to examine the thermal stability of the fine-grained structure produced by EX-ECAP. Tensile testing was conducted on the fine-grained alloy at elevated temperatures. It is shown that both low temperature superplasticity and high strain rate superplasticity are attained for the fine-grained sample.