OBJECTIVE To study the effect of fluoroquinolones on the level of transcription of norA gene in Staphylococcus aureus(SAU).METHODS The accumulation of fluoroquinolones in SAUz and its induced resistant strain(SAUz-16) and the effect of carbonyl cyanide m-chlorophenylhydrazone(CCCP) on accumulation were studied by fluorescence measured method.The level of transcription of norA gene was studied by slot blot hybridization.RESULTS The steady-state accumulation of SAUz-16 was lower than that of its parent(SAUz).The accumulation of hydrophilic fluoroquinolones in SAUz-16 increased obviously when CCCP was added,but it is lower than that of SAUz.The level of transcription of norA gene in SAUz-16 was higher than that of SAUz.CONCLUSIONS Fluoroquinolones can increase the level of transcription of norA gene.The increase in efflux of hydrophilic fluoroquinolones resulted from the increase in transcription of norA gene is one of causes of decrease in the accumulation of drugs in S.aureus.