Gemifloxacin is a broad spectrum antibiotic and belongs to fourth generation of fluoroquinolone class.It has shown excellent coverage against wide variety of pathogenic micro organisms causing diseases in animals and humans.In this study,an attempt was made to evaluate the immunomodulatory potential of gemifloxacin in male swiss albino mice in vivo.Three doses of gemifloxacin 25mg/kg,50mg/kg and 75mg/kg were used i.p.for the evaluation of immune responses in mice.Delayed Type Hypersensitivity(DTH)assay has shown the significant immune suppressant potential of gemifloxacin at 25 mg/kg dose and 75mg/kg dose.Total leukocyte count(TLC)has shown decrease in leukocyte count(P<0.05)in drug treatment groups before cyclophosphamide administration and very highly significant decrease(P<0.001)in leukocyte count after cyclophosphamide administration as compared to negative control group.Differential leukocyte count(DLC)has shown very highly significant decrease(P<0.001)in percentage count of lymphocytes in 75mg/kg treatment group in leukopenic mice while increase(P<0.001)in monocytes count before cyclophosphamide administration in treatment group 50 mg/kg and 75mg/kg was observed.Increase(P<0.01)in monocytes percentage in 50 mg/kg treatment group in leukopenic mice and increase in neutrophil percentage count(P<0.05)in all treatment groups after cyclophosphamide administration was observed.Humoral immune response was shown to be suppressed in dose dependant manner by both Heamagglutination titre values(P<0.001)and jerne hemolytic plaque formation assay(P<0.001).The results of this basic research work clearly demonstrate the immunomodulatory potential of gemifloxacin that might be considered while using gemifloxacin in the treatment of infectious diseases in animals including wildlife animals.