High temperature deformation behavior of AZ31 Mg alloy was investigated in this study on the basis of a processing map (epsilon approximate to 0.6). To construct a processing map, compression tests were carried out at various temperatures and strain rates. Two regions of high deformation efficiency (eta) were identified as: (1) a dynamic recrystalization (DRX) domain at 250 degrees C and 1/s and (2) a superplasticity domain at 450 degrees C and 10(-4)/s. The average gain size observed in the DRX region was considerably smaller (2.9 mu m) than in any other region. In the superplastic condition, tensile elongation to failure approached to 1040%. At the high Z regions, flow softening occurred resulting from the dynamic recrystallization but below 10(10) of Z value, flow hardening occurred due to the grain growth. Possible deformation mechanisms operating at high temperature were discussed in relation to the activation energy. A two-stage deformation method was found to be effective in enhancing the superplasticity of AZ31 Mg alloy.