The effects of solution treatment (T4) on the in vitro corrosion properties were investigated for Mg-2Gd-xAg (x=l, 2 wt. %), Mg-2Gd-xCa (x=0.4, 0.8 wt. %) alloys. The cytocompatibility of pure Mg, Mg-2Gd, Mg-2Gd-2Ag and Mg-2Gd-0.8Ca alloy was studied as well. All alloys were prepared by permanent mould casting. T4 heat treatment was carried out at 510 °C for 48 h under Ar atmosphere and specimens were quenched in water at room temperature. Corrosion experiments were performed in cell culture medium under cell culture conditions. Cytocompatibility was evaluated by direct cell adhesion and live/dead staining tests. After T4 heat treatment, the amount of intermetallic phases is significantly decreased, which leads to significant improvement of corrosion properties by a very high factor (5-30). The results of live/dead staining reveal that the cells are mostly in viable state and homogenously distributed over the surface. The corrosion layer shows no cytotoxicity to primary human osteoblasts.