The high temperature workability of the ZEK200 Mg-alloy produced by Direct Chill casting (DC) was investigated by torsion testing between 200 and 450°C. The alloy exhibited a higher strength and a slightly lower equivalent strain to fracture than AZ31 and ZM21 produced by DC. The calculation of the constitutive equation gave a value of the activation energy for high temperature deformation close to 175 kJ/mol, in line with those calculated by following the same procedure in AZ31 and ZM21. Partial or complete recrystallization of the deformed structure was observed at 350 and 400°C respectively. Grain growth occurred after recrystallization in the samples tested at 450°C.