Corrosion fatigue data for magnesium alloys are still scarce. The present communication reports the results of microstructural investigations and fatigue testing of the fine grain Mg-Zn-Zr (ZK60) alloy after multiaxial isothermal forging and of the hot extruded Mg-Y-Zn (WZ21) alloy in air and in the 0.9% NaCl water solution. Both of the alloys demonstrate a very good high-cycle fatigue performance in air. However, the significant drop of fatigue resistance is observed in the corrosive environment. Results are discussed from perspectives of potential applications and future studies.