2, 6-Disubstituted-3-pyridazinones were synthesized from the reaction of trichloroethylideneacetophenone with substituted phenylhydrazines. Trichloroethylideneacetophenone 2, 4-dinitrophenylhydrazone was isolated from the reaction of trichloroethylideneacetophenone with 2, 4-dinitrophenylhydrazine and it gave 2-(2, 4-dinitrophenyl)-6-phenyl-3-pyridazinone through ring closure. This indicates that pyridazinones are produced through hydrazone formation and ring closure as suggested previously. The effect of substituents of phenylhydrazine on the reaction was also discussed.