The biosynthesis and function of flagella is positively regulated by the cyclic AMP-catabolite activator protein (cAMP-CAP) complex and the nucleoid protein H-NS. In this report, we show that nonmotile Salmonella typhimurium hns mutants could recover its motility by introducing the rpoSmutation. In a swarm plate assay, rpoS/hns double mutants could woim while hns mutants could not. This regeneration of motility resulted from the flagella synthesis. Transmission electron microscopy analysis showed the capability of rpoS/hns double mutants for flagella synthesis. And rpoS mutation derepressed the transcription of flhD, the flagella master gene, in hns mutants.