A commercially processed SUPRAL 100(AA2004) sheet material of nominal composition: Al-6wt%Cu-0.4wt%Zr, has been deformed in-situ in a field emission gun scanning electron microscope at a temperature of 450degreesC at strain rates of (1similar to2.5)x10(-4)s(-1) to a total elongation of similar to100%. The microstructural evolution in the surface of the specimen was monitored during deformation. Straining was stopped at intervals to allow high resolution EBSD measurements to be made and the evolution of texture, grain size and the fraction of high angle grain boundaries was obtained. It was found that the fraction of high angle grain boundaries increased with strain and consequently a fine grain superplastic (SP) microstructure developed at a true strain of about 0.5. A previous model for geometrical dynamic recrystallization was found to satisfactorily describe the characteristics of the microstructural evolution.