Abstract: The anticonvulsive activity of three kinds of pyrazolidinones:5-benzyl- substitut-ed-3-pyrazolidinones;5-benzyl-1-alkyl substituted and 1-alkyl substituted-3-pyrazolidinones werestudied. Fourteen substitutes of these three kinds of pyrazolidinones were found to be potent anticonvul-sants.In doses less than TD₅₀,they were found to be able to protect mice and rats from seizuresproduced by maximal electroshock seizure(MES),such action appeared rapidly and lasted for a shortperiod。II-f was shown to be the most potent anti-MES agent among these three kinds of pyrazolidi-nones.It also showed therapeutic effect in treating experimental epilepsy produced by intrahippocam-pal injection of zinc sulfate in rabbits and audiogenic seizures in rats.The third kind of pyrazolidinonesa1so showed anti-metrazol induced seizures in mice.