A ZK60 magnesium alloy was subjected to isothermal rolling (IR) at 275 and 300degreesC. This processing resulted in grain refinement through dynamic recrystallization (DRX) at both temperatures. The recrystallized volume fractions of 82 and 95% and average sizes of fine grains of 2.5 and 3.7 mum were achieved after IR at 275 and 300degreesC, respectively. It was shown that the ultrafine-grained structure produced by DRX at 300degreesC exhibited higher stability under following static and dynamic annealing than that produced at 275degreesC. This fact was attributed with the formation of a less constrained DRX structure at higher temperature of IR. As a result, the sheet produced from the ZK60 alloy at 300degreesC showed superior superplastic properties. Conversely, it was not feasible to enhance the superplastic properties in the ultrafine-grained alloy produced at 275degreesC because significant grain growth occurred during further processing of the as-rolled alloy.