Fine grain size is a microstructural requirement for superplastic alloys. We now have a general understanding of the methods of grain refinement and of restriction of grain coarsening. Phase transformation, recrystallation, deformation of duplex microstructures, and phase separation in duplex alloys can produce grain refinement, while particle dispersions and partitioning in duplex microstructures are useful methods for restricting grain coarsening. The methods selected for grain refinement and grain coarsening control for a specific alloy depend on the character of the alloy. Application of several of these methods to grain refinement and grain coarsening control in high-strength aluminum alloys is discussed.