It has been reported that the creep resistance of AE42 tends to deteriorate at temperatures above 150°C while AE44 exhibits much better creep performance at elevated temperatures. However, the relationship between microstructure and creep resistance in these Mg-Al-RE die-casting alloys has not been well understood. In the present work, the microstructures and creep behaviour of AE42 and AE44 die-casting alloys were investigated and compared. The creep tests were conducted at 175°C in a stress range of 75 - 110 MPa. The microstructures in the as-cast and aged conditions were characterised in detail by transmission electron microscopy (TEM). The correlation between creep resistance and microstructure suggests that the level of Al solute retained in the a-Mg matrix after die-casting is an important factor in influencing creep resistance, with high levels leading to the subsequent precipitation of Mg 17Al12 during creep and the deterioration of creep resistance.