The reaction of 5-amino-3-cyano-1-(2, 6-dichloro-4-trifluoromethylphenyl) -1H-pyrazole and 5-amino-1-[2, 6-dichloro-4-(trifluoromethylphenyl]-4-trifluoromethylsulfinyl-1H-pyrazole-3-carbonitrile (Fipronil) with arylsulfonyl chlorides gave the 5-arylsulfonamides at room temperature in high yields. Some of these compounds had insecticidal activity against pests such as army worm and rice plant hopper.