Japanese encephalitis viruses (JEV) were well propagated in human glioma cells, 118 MGC until the first 24hrs after virus infection. However, after 24hrs, virus growth rate was quickly reduced. This unusual pattern of virus growth was different from the cases in others cells, e. g. IMR-32, Vero and C6/36 cells. The fact that actinomycin-D retained the high yields of JEV in 118 MGC cells suggests that some suppressing factors against JEV replication are produced in MGC cells. Interestingly, culture fluids of 118 MGC cells indicated inhibitory effect to JEV reproduction, but other culture fluids from several cell lines had no effect. This inhibitory effect of the MGC-culture fluids was lost by heat-treatment at 60 C. In addition, the infectivity of JEV was rapidly decreased by the incubation with MGC-culture fluids. These findings suggest that 118 MGC cells produce and secret some inhibitory factors against JEV replication.