Surface nanocrystallization in various steels by shot peening (both air blast and ultrasonic) and particle impact processing was investigated. Nanocrystalline layers with several mum thick were successfully fabricated by these methods. In all the case, the nanocrystalline layers have extremely high hardness and separated from adjacent deformed structure regions with sharp boundaries. By annealing, the nanocrystalline layers showed substantially slow grain growth without recrystallization. Those characteristics are similar to those observed in the samples experienced ball milling and ball drop deformation.