Particle-stimulated nucleation (PSN) was investigated in magnesium alloy AZ31 to study the effect of the evolution of second-phases during extrusion and other metal forming processes. Compression tests were carried out on samples taken from coarse-grained as-cast magnesium alloy billets containing a lamellar Mg(17)Al(12) eutectic phase and (Al, Mn) particles. These revealed that particle-stimulated DRX nucleation (PSN) was taking place during hot deformation and that this is facilitated by the fragmentation of the Mg(17)Al(12). When Mg(17)Al(12) dissolves into the matrix at about 350 degrees C, the (Al, Mn) particles remain effective in producing PSN at temperatures up to at least 400 degrees C. This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.