Hot extrusion has been carried out at 573, 673 and 753 K on machined chips of an AZ91 magnesium alloy and mechanical properties of the extrusions have been investigated. The extrusions processed from machined chips showed a good combination of high ultimate tensile strengths of 320∼410 MPa, high 0.2% proof stresses of 220∼300 MPa and elongations to failure of 5∼12% at room temperature. Grain refinement and dispersion of oxide layers by hot extrusion were responsible for the good mechanical properties at room temperature. Also the extrusions processed from machined chips at 573 and 673 K showed superplastic behavior at 573 K, though the elongations of the extrusions processed from machined chips were lower than those of the extrusion processed from the cast ingot.