Antiviral activity against Japanese B encephalitis virus and rabies-fixed virus was examined with the following five kinds of diaryl sulfone compounds prepared in the present series of work, bis[4-(4-hydroxyphenylazo) phenyl] sulfone, bis[4-(2-butenylidene)-hydrazinophenyl] sulfone, bis[4-(1-carboxyethyliedne) hydrazinophenyl] sulfone, bis[4-(1-methyl-3-carboxypropylidene) hydrazinophenyl] sulfone, and bis(4-cyclohexylidenehydrazinophenyl) sulfone, together with 21 kinds of componds which were described in previous papers. None of these compounds showed inactivation of the viruses.