This work studied the effect of extrusion and alloying with 4 wt.% of Zn and 0.4 wt.% of Ca on the structure and mechanical properties of magnesium. Light, scanning electron microscopy, X-ray diffraction, hardness, compressive and tensile tests were used for this purpose. The addition of zinc led to the formation of MgZn and further alloying with calcium changed the nature of the secondary phase to Ca2Mg6Zn3. The process of extrusion resulted in significant structural refinement, which was the most pronounced for the Mg-4Zn-0.4Ca alloy. In this alloy the average grain size was 6 µm. The extrusion improved all the measured characteristics and the most pronounced improvement was observed in the case of tensile yield strength. The presence of calcium improved the positive effect of zinc on the mechanical properties of magnesium. Differences in the mechanical behaviour of magnesium and its alloys were discussed in relation to structural variations resulting in different strengthening effects.K e y w o r d s : magnesium alloys, microstructure, extrusion, mechanical properties