Several vinylsulfonylphenyl triketones and 2-alkoxy- and 2-(N,N-diethylamino) ethanesulfonylphenyl triketones have been synthesized, and their herbicidal activities in flooded paddy field were studied. Herbicidal effects of vinylsulfonyl triketones 6a-c were not satisfactory, whereas 2-alkoxyethanesulfonylphenyl triketones 7a and 7b showed good herbicidal activities without meaningful selectivity to rice.