Abstract: The juice squeezed from fresh celery leaves has long been used in southeastern China for the treatment of epilepsy. This effect has aroused interest in the medical profession in China. Yang and Chen of our institute isolated two active compounds, Ag-1 and Ag-2 from the seeds of the plant Apium graveolens Linn. All of them contain no nitrogen atom in their molecules. We found that Ag-1, Ag-2 and synthetic d,1-Ag-1 produced very similar protective action against MES, MET, MST and MAS in mice and rats with doses lower than their TD₅₀. The ip TD₅₀ of d, 1-Ag-1 was found to be 438±6.1 mg/kg in mice and 360±7.3 mg/kg in rats. ED₅₀ of this compound was found to be 75±8.9 mg/kg in mice and 76±3.8 mg/kg in rats.