The inhibitory effect of thiazole-thiourea derivatives on poliovirus and adenovirus replication was investigated by the tissue culture method. Among the compounds tested, 1-phenyl-3-(2-thiazolyl)thiourea, (4-methyl-2-thiazolyl)thiourea, 1-p-tolyl-3-(4-methyl-2-thiazolyl) thiourea, 1-m-chlorophenyl-3-(4-methyl-2-thiazolyl)thiourea, 1-benzoyl-3-(4-methyl-2-thiazolyl)thiourea, 1-p-tolyl-3-(4-phenyl-2-thiazolyl)thiourea, and 1-p-chlorophenyl-3-(4-phenyl-2-thiazolyl)thiourea exerted a clear inhibition of the CPE and multiplication of polio virus, and 1-p-tolyl-3-(2-thiazolyl)thiourea, (4-methyl-2-thiazolyl)thiourea, 1-phenyl-3-(4-methyl-2-thiazolyl)thiourea, 1-p-chlorophenyl-3-(4-methyl-2-thiazolyl)thiourea, 1-benzoyl-3-(4-methyl-2-thiazolyl)thiourea, 1-phenyl-3-(4-phenyl-2-thiazolyl)thiourea, and 1-p-chlorophenyl-3-(4-phenyl-2-thiazolyl)thiourea showed antivira1 activity against adenovirus.