1100 commercial purity aluminum was highly strained up to a total equivalent strain of 4.8 by ARB process at 473K. The ARB processed sheet was filled with the pancake shaped ultrafine grains whose mean thickness and length are 270 nm and 1.2 mum, respectively. The elongated ultrafine grains including dislocations were surrounded by high-angle boundaries, so that this structure could be considered as a kind of recrystallized grain structure as well as a deformed structure. Microstructural change of the ultrafine grains during annealing was investigated by TEM including in-situ observation. It was clarified that recovery within the grains dominantly occurs at lower temperature and then normal grain growth of the ultrafine grains takes place at higher temperatures.