Abstract: Objective Developing a rapid assay of susceptibility of neisseria gonorrhoeae(Ng)to ciprofloxacin(CIPF).Methods After treated with CIPF,12 strains Ng was detected by flow cytometry,and these data were analysed by double-parameters.Results The mean fluorescence channel(FL3 log)of living Ng and dead Ng killed by heat was 0.43 and 75.7 respectively.We determined 12 strains Ng incubatd with 2μg/ml CIPF for 2h at 37℃ by flow cytometry,and the results were that the rate of dead bacteria of 6 strains CIPF resistant Ng and 6 strains CIPF susceptible Ng were(14.1±4.5)% AND(40.1±5.8)% respectively,which were significantly differnet(P0.001).The mean fluorescance channel of dead bacteria of 6 strains CIPF resistact Ng and 6 strains CIPE susceptible Ng were(14.1±4.5) and(40.1±5.8)respectively,which were also significiently different(P<0.05).Conclusion Rapid assay Ng susceptibility to CIPF can be achieved by flow cytometry.