A selected group of alkoxy- and halogen-substituted 5-benzylidino- and 5-benzylhydantoins was prepared and screened for anticonvulsant activity as measured by the ability of the compound to prevent maximal electroshock and metrazol-induced threshold clonic seizures in rats. The structure-activity studies revealed 5-[3-(trifluoromethyl)benzyl]hydantoin (14) to be the most potent member of the series.