Grain refinement taking place during equal channel angular pressing (ECAP) was studied in a commercial Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 450 degrees C. Inhomogeneous deformation occurring during hot ECAP of the present alloy leads to formation of deformation bands. Repeated ECAP results in mutual crossing and increase in number and misorientation of deformation bands, followed by transformation of boundaries of deformation bands into high angle boundaries. As a result, a new fine-grained microstructure with an average crystallite size of 2.8 mu m develops at large strains above 8. It is concluded that grain refinement occurs in accordance with deformation-induced continuous reactions; that is essentially similar to continuous dynamic recrystallization. The mechanisms of new grain evolution, as well as factors promoting grain refinement, are discussed in detail.