Uniaxial hot compression tests were performed at constant temperature (T) and strain rate (ε& ) in the ranges of 200-500 °C at an interval of 50 °C and 0.001-20 s-1. The flow stress data were used to develop the extrusion limit diagram for AZ31 and AM30 magnesium tubes. The extrusion limit diagram shows a wide region available for extruding AZ31 and AM30 seamless tubes, and comparison of the two extrusion limit diagrams shows that, the extrudability of AM30 alloy is better than that of AZ31 alloy. Actual extrusion trials validated the predicted temperature rise limit curve corresponding to the occurrence of surface cracking during the extrusion process. Magnesium tubes were successfully extruded according to the safe regions identified by the extrusion limit diagram.