Evidence on cooperative phenomena including sliding and rotation of grain groups and correlated grain boundary migration during superplastic deformation under different strain states is reported. The pattern of macroscopic surfaces at which grain blocks slide as an entity is consistent with that of dip lines predicted by the slip band field theory. Sliding of grains at these shear surfaces occurs in a sequential manner. Increasing strain and applied stress (strain rate) result in decrease in spacing of the shear surfaces. Cooperative grain rotation results in a change in the orientation of the macroscopic shear surfaces and provides accommodation sliding of grain group. Correlated grain boundary migration is due to the coupling of grain boundary sliding and migration caused by characteristics of dislocation movement at grain boundaries.