Tension–compression asymmetry in Mg–8Al–0.5Zn alloys has been studied as a function of precipitation state. It has been shown that the presence of precipitates significantly reduces yield asymmetry compared with solution treated material. This reduction in asymmetry was attributed to reduced rates of twinning in the presence of Mg 17 Al 12 precipitates. This has been confirmed by texture and microstructure analyses, which show a reduction in the scale and volume fraction of twins in aged and solution treated samples examined at equivalent levels of strain.